Apparatus and methods for electrosurgical removal and digestion of tissue

ABSTRACT

Electrosurgical methods, systems, and apparatus for the controlled ablation of tissue from a target site of a patient. An electrosurgical apparatus of the invention includes an active electrode assembly having an active electrode screen surrounded by a plurality of flow protectors. Each flow protector defines a shielded region of the active electrode screen, each shielded region of the screen characterized by enhanced plasma formation. The active electrode assembly is adapted for removing tissue from a surgical site, and the active electrode screen is adapted for digesting fragments of resected tissue. In one embodiment, the apparatus is particularly suited to simultaneously removing both hard and soft tissue in, or around, a joint.

RELATED APPLICATIONS

[0001] The present application is a non-provisional of U.S. ProvisionalApplication No. 60/326,516, filed on Oct. 2, 2001, and is acontinuation-in-part of U.S. patent application Ser. No. 09/836,940filed Apr. 17, 2001 (Attorney Docket No. A-14-3) which is acontinuation-in-part of U.S. patent application Ser. No. 09/766,168,filed Jan. 19, 2001 (Attorney Docket No. A-14-2), which is acontinuation-in-part of U.S. patent application Ser. No. 09/758,403filed Jan. 10, 2001 (Attorney Docket No. A-14-1), which claims priorityfrom U.S. Provisional Patent Application No. 60/233,345 filed Sep. 18,2000 (Attorney Docket No. A-14-1P), and is a continuation-in-part ofU.S. patent application Ser. No. 09/709,035 filed Nov. 8, 2000 (AttorneyDocket No. A-14), which claims priority from U.S. Provisional PatentApplication No. 60/210,567 filed Jun. 9, 2000 (Attorney Docket No.A-14P), and is a continuation-in-part of U.S. patent application Ser.No. 09/197,013, filed Nov. 20, 1998 (Attorney Docket No. A-6-1), whichis a continuation-in-part of U.S. patent application Ser. No.09/010,382, filed Jan. 21, 1998, now U.S. Pat. No. 6,190,381 (AttorneyDocket No. A-6).

[0002] The present invention is related to commonly assigned co-pendingProvisional Patent Application No. 60/062,997 filed on Oct. 23, 1997(Attorney Docket No. 16238-007400), non-provisional U.S. patentapplication Ser. No. 08/977,845, filed Nov. 25, 1997, now U.S. Pat. No.6,210,402 (Attorney Docket No. D-2), which is a continuation-in-part ofapplication Ser. No. 08/562,332, filed Nov. 22, 1995, now U.S. Pat. No.6,024,733 (Attorney Docket No. 016238-000710), the complete disclosuresof which are incorporated herein by reference for all purposes. Thepresent invention is also related to U.S. patent application Ser. Nos.09/109,219, 09/058,571, 08/874,173 and 09/002,315, filed on Jun. 30,1998, Apr. 10, 1998, Jun. 13, 1997, and Jan. 2, 1998, respectively(Attorney Docket Nos. CB-1, CB-2, 16238-005600 and C-9, respectively)and U.S. patent application Ser. No. 09/054,323, filed on Apr. 2, 1998(Attorney Docket No. E-5), now U.S. Pat. No. 6,063,079, U.S. patentapplication Ser. No. 09/010,382, filed Jan. 21, 1998, now U.S. Pat. No.6,190,381, (Attorney Docket A-6), and U.S. patent application Ser. No.09/032,375, filed Feb. 27, 1998, (Attorney Docket No. CB-3), U.S. patentapplication Ser. No. 08/977,845, filed on Nov. 25, 1997, now U.S. Pat.No. 6,210,402 (Attorney Docket No. D-2), Ser. No. 08/942,580, filed onOct. 2, 1997, now U.S. Pat. No. 6,159,194 (Attorney Docket No.16238-001300), U.S. application Ser. No. 08/753,227, filed on Nov. 22,1996, now U.S. Pat. No. 5,873,855 (Docket 16238-002200), U.S.application Ser. No. 08/687,792, filed on Jul. 18, 1996, now U.S. Pat.No. 5,843,019 (Docket No. 16238-001600), the complete disclosures ofwhich are incorporated herein by reference for all purposes. The presentinvention is also related to commonly assigned U.S. Pat. No. 5,683,366,filed Nov. 22, 1995 (Attorney Docket 16238-000700), the completedisclosure of which is incorporated herein by reference for allpurposes.

BACKGROUND OF THE INVENTION

[0003] The present invention relates generally to the field ofelectrosurgery, and more particularly to surgical devices and methodswhich employ high frequency electrical energy to resect, coagulate,ablate, and aspirate cartilage, bone and other tissue, such as sinustissue, adipose tissue, or meniscus, cartilage, and synovial tissue in ajoint. The present invention also relates to apparatus and methods foraggressively removing tissue at a target site by a low temperatureablation procedure, and efficiently aspirating products of ablation fromthe target site. The present invention further relates to anelectrosurgical probe having a flow protection element for promotingplasma formation.

[0004] Conventional electrosurgical methods generally reduce patientbleeding associated with tissue cutting operations and improve thesurgeon's visibility. These electrosurgical devices and procedures,however, suffer from a number of disadvantages. For example, monopolarelectrosurgery methods generally direct electric current along a definedpath from the exposed or active electrode through the patient's body tothe return electrode, which is externally attached to a suitablelocation on the patient's skin. In addition, since the defined paththrough the patient's body has a relatively high electrical impedance,large voltage differences must typically be applied between the activeand return electrodes to generate a current suitable for cutting orcoagulation of the target tissue. This current, however, mayinadvertently flow along localized pathways in the body having lessimpedance than the defined electrical path. This situation willsubstantially increase the current flowing through these paths, possiblycausing damage to or destroying tissue along and surrounding thispathway.

[0005] Bipolar electrosurgical devices have an inherent advantage overmonopolar devices because the return current path does not flow throughthe patient beyond the immediate site of application of the bipolarelectrodes. In bipolar devices, both the active and return electrode aretypically exposed so that they may both contact tissue, therebyproviding a return current path from the active to the return electrodethrough the tissue. One drawback with this configuration, however, isthat the return electrode may cause tissue desiccation or destruction atits contact point with the patient's tissue.

[0006] Another limitation of conventional bipolar and monopolarelectrosurgery devices is that they are not suitable for the preciseremoval (ablation) of tissue. For example, conventional electrosurgicalcutting devices typically operate by creating a voltage differencebetween the active electrode and the target tissue, causing anelectrical arc to form across the physical gap between the electrode andtissue. At the point of contact of the electric arcs with tissue, rapidtissue heating occurs due to high current density between the electrodeand tissue. This high current density causes cellular fluids to rapidlyvaporize into steam, thereby producing a “cutting effect” along thepathway of localized tissue heating. The tissue is parted along thepathway of vaporized cellular fluid, inducing undesirable collateraltissue damage in regions surrounding the target tissue site.

[0007] In addition, conventional electrosurgical methods are generallyineffective for ablating certain types of tissue, and in certain typesof environments within the body. For example, loose or elasticconnective tissue, such as the synovial tissue in joints, is extremelydifficult (if not impossible) to remove with conventionalelectrosurgical instruments because the flexible tissue tends to moveaway from the instrument when it is brought against this tissue. Sinceconventional techniques rely mainly on conducting current through thetissue, they are not effective when the instrument cannot be broughtadjacent to or in contact with the elastic tissue for a long enoughperiod of time to energize the electrode and conduct current through thetissue.

[0008] The use of electrosurgical procedures (both monopolar andbipolar) in electrically conductive environments can be furtherproblematic. For example, many arthroscopic procedures require flushingof the region to be treated with isotonic saline, both to maintain anisotonic environment and to keep the field of view clear. However, thepresence of saline, which is a highly conductive electrolyte, can causeshorting of the active electrode(s) in conventional monopolar andbipolar electrosurgery. Such shorting causes unnecessary heating in thetreatment environment and can further cause non-specific tissuedestruction.

[0009] Conventional electrosurgical cutting or resecting devices alsotend to leave the operating field cluttered with tissue fragments thathave been removed or resected from the target tissue. These tissuefragments make visualization of the surgical site extremely difficult.Removing these tissue fragments can also be problematic. Similar tosynovial tissue, it is difficult to maintain contact with tissuefragments long enough to ablate the tissue fragments in situ withconventional devices. To solve this problem, the surgical site isperiodically or continuously aspirated during the procedure. However,the tissue fragments often clog the aspiration lumen of the suctioninstrument, forcing the surgeon to remove the instrument to clear theaspiration lumen or to introduce another suction instrument, whichincreases the length and complexity of the procedure.

[0010] During certain electrosurgical procedures, for example inprocedures which involve aspiration of relatively large volumes of fluidfrom a target site, generating and maintaining a plasma from anelectrically conductive fluid in the vicinity of the active electrodecan be problematic. This situation may be exacerbated by splitting powerfrom the power supply between two different types of active electrode,e.g. an active electrode terminal adapted for aggressively removingconnective tissue, such as ligament, tendon and cartilage, and an activeelectrode screen adapted for digestion of resected tissue fragments. Thepresent invention overcomes problems related to generating andmaintaining a plasma by providing a flow protection unit to provideregions of an active electrode assembly that are at least partiallyshielded from flow of an aspiration stream.

[0011] Furthermore, in certain electrosurgical procedures of the priorart, for example, removal or resection of the meniscus duringarthroscopic surgery to the knee, it is customary to employ twodifferent tissue removal devices, namely an arthroscopic punch and ashaver. There is a need for an electrosurgical apparatus which enablesthe aggressive removal of relatively hard tissues (e.g.fibrocartilaginous tissue) as well as soft tissue, and which is adaptedfor aspirating resected tissue, excess fluids, and ablation by-productsfrom the surgical site. The instant invention provides a single devicewhich can replace the punch and the shaver of the prior art, whereintissue may be aggressively removed according to a low temperatureablation procedure, and resected tissue can be efficiently removed by acombination of aspiration from the site of tissue resection anddigestion of resected tissue fragments.

SUMMARY OF THE INVENTION

[0012] The present invention provides systems, apparatus, kits, andmethods for selectively applying electrical energy to target tissue of apatient. In particular, methods and apparatus are provided forresecting, cutting, partially ablating, aspirating or otherwise removingtissue from a target site, and ablating the tissue in situ.

[0013] In one aspect, the present invention provides an electrosurgicalinstrument for treating tissue at a target site. The instrumentcomprises a shaft having a proximal portion and a distal end portion.One or more active loop electrodes are disposed at the distal end of theshaft. The loop electrodes preferably have one or more edges thatpromote high electric fields. A connector is disposed near the proximalend of the shaft for electrically coupling the active loop electrodes toa high frequency source.

[0014] The active loop electrodes typically have an exposed semicircularshape that facilitates the removing or ablating of tissue at the targetsite. During the procedure, bodily fluid, non-ablated tissue fragmentsand/or air bubbles are aspirated from the target site to improvevisualization.

[0015] At least one return electrode is preferably spaced from theactive electrode(s) a sufficient distance to allow a relativelyhomogeneous electrical field distribution on the active electrode(s) andto prevent arcing therebetween at the voltages suitable for tissueremoval and or heating, and to prevent contact of the returnelectrode(s) with the tissue. The current flow path between the activeand return electrodes may be generated by immersing the target sitewithin electrically conductive fluid (as is typical in arthroscopicprocedures), or by directing an electrically conductive fluid along afluid path past the return electrode and to the target site (e.g., inopen procedures). Alternatively, the electrodes may be positioned withina viscous electrically conductive fluid, such as a gel, at the targetsite, and submersing the active and return electrode(s) within theconductive gel. The electrically conductive fluid will be selected tohave sufficient electrical conductivity to allow current to passtherethrough from the active to the return electrode(s), and such thatthe fluid ionizes into a plasma when subject to sufficient electricalenergy, as discussed below. In the exemplary embodiment, the conductivefluid is isotonic saline, although other fluids may be selected, asdescribed in co-pending Provisional Patent Application No. 60/098,122,filed Aug. 27, 1998 (Attorney Docket No. CB-7P), the complete disclosureof which is incorporated herein by reference.

[0016] In a specific embodiment, tissue ablation results from moleculardissociation or disintegration processes. Conventional electrosurgeryablates or cuts through tissue by rapidly heating the tissue untilcellular fluids explode, producing a cutting effect along the pathway oflocalized heating. The present invention volumetrically removes tissue,e.g., cartilage tissue, in a cool ablation process known as Coblation®,wherein thermal damage to surrounding tissue is minimized. During thisprocess, a high frequency voltage applied to the active electrode(s) issufficient to vaporize an electrically conductive fluid (e.g., gel orsaline) between the electrode(s) and the tissue. Within the vaporizedfluid, a plasma is formed and charged particles (e.g., electrons andions) cause the molecular breakdown or disintegration of tissuecomponents in contact with the plasma. This molecular dissociation isaccompanied by the volumetric removal of the tissue. This process can beprecisely controlled to effect the volumetric removal of tissue as thinas 10 to 50 microns with minimal heating of, or damage to, surroundingor underlying tissue structures. A more complete description of thisCoblation® phenomenon is described in commonly assigned U.S. Pat. No.5,683,366, the complete disclosure of which is incorporated herein byreference.

[0017] The present invention offers a number of advantages overconventional electrosurgery, microdebrider, shaver and laser techniquesfor removing soft tissue in arthroscopic, sinus or other surgicalprocedures. The ability to precisely control the volumetric removal oftissue results in a field of tissue ablation or removal that is verydefined, consistent and predictable. In one embodiment, the shallowdepth of tissue heating also helps to minimize or completely eliminatedamage to healthy tissue structures, e.g., cartilage, bone and/or nervesthat are often adjacent the target tissue. In addition, small bloodvessels at the target site are simultaneously cauterized and sealed asthe tissue is removed to continuously maintain hemostasis during theprocedure. This increases the surgeon's field of view, and shortens thelength of the procedure. Moreover, since the present invention allowsfor the use of electrically conductive fluid (contrary to prior artbipolar and monopolar electrosurgery techniques), isotonic saline may beused during the procedure. Saline is the preferred medium for irrigationbecause it has the same concentration as the body's fluids and,therefore, is not absorbed into the body as much as certain otherfluids.

[0018] Systems according to the present invention generally include anelectrosurgical instrument having a shaft with proximal and distal endportions, one or more active loop electrode(s) at the distal end of theshaft and one or more return electrode(s). The system can furtherinclude a high frequency power supply for applying a high frequencyvoltage difference between the active electrode(s) and the returnelectrode(s). The instrument typically includes an aspiration lumenwithin the shaft having an opening positioned proximal of the activeelectrode(s) so as to draw bodily fluids and air bubbles into theaspiration lumen under vacuum pressure.

[0019] In another aspect, the present invention provides anelectrosurgical probe having a fluid delivery element for deliveringelectrically conductive fluid to the active electrode(s) and the targetsite. The fluid delivery element may be located on the instrument, e.g.,a fluid lumen or tube, or it may be part of a separate instrument. In anexemplary configuration the fluid delivery element includes at least oneopening that is positioned around the active electrodes. Such aconfiguration provides an improved flow of electrically conductive fluidand promotes more aggressive generation of the plasma at the targetsite.

[0020] Alternatively, an electrically conductive fluid, such as a gel orliquid spray, e.g., saline, may be applied to the tissue. Inarthroscopic procedures, the target site will typically already beimmersed in a conductive irrigant, i.e., saline. In these embodiments,the apparatus may lack a fluid delivery element. In both embodiments,the electrically conductive fluid will preferably generate a currentflow path between the active electrode(s) and the return electrode(s).In an exemplary embodiment, a return electrode is located on theinstrument and spaced a sufficient distance from the active electrode(s)to substantially avoid or minimize current shorting therebetween and toshield the tissue from the return electrode at the target site.

[0021] In another aspect, the present invention provides a method forapplying electrical energy to a target site within or on a patient'sbody. The method comprises positioning one or more active electrodesinto at least close proximity with the target site. An electricallyconductive fluid is provided to the target site and a high frequencyvoltage is applied between the active electrodes and a return electrodeto generate relatively high, localized electric field intensitiesbetween the active electrode(s) and the target site, wherein anelectrical current flows from the active electrode(s) through tissue atthe target site. The active electrodes are moved in relation to thetargeted tissue to resect or ablate the tissue at the target site.

[0022] In another aspect, the present invention provides anelectrosurgical system for removing tissue from a target site to betreated. The system includes a probe and a power supply for supplyinghigh frequency alternating current to the probe. The probe includes ashaft, an ablation electrode, and a digestion electrode, wherein theablation electrode and the digestion electrode are independently coupledto opposite poles of the power supply. Typically, the probe andelectrosurgical system lack a dedicated return electrode. Instead, theablation and digestion electrodes can alternate between serving asactive electrode and serving as return electrode, i.e., the power supplycan alternate between preferentially supplying electric power to theablation electrode and preferentially supplying electric power to thedigestion electrode. When power is preferentially supplied to theablation electrode, the ablation electrode functions as an activeelectrode and is capable of ablating tissue, while the digestionelectrode serves as a return electrode. When power is preferentiallysupplied to the digestion electrode, the digestion electrode functionsas an active electrode and is capable of ablating tissue, while theablation electrode serves as a return electrode. Thus, both the ablationelectrode and the digestion electrode are adapted for ablating tissue,albeit under different circumstances. Namely, the ablation electrode isadapted for removing tissue from a site targeted for treatment, whereasthe digestion electrode is adapted for digesting tissue fragmentsresected from the target site by the ablation electrode. Thus, the twoelectrode types (ablation and digestion electrodes) operate in concertto conveniently remove, ablate, or digest tissue targeted for treatment.It should be noted that the mechanism involved in removing tissue by theablation electrode and in digesting tissue fragments by the digestionelectrode may be essentially the same, e.g., a cool ablation processinvolving the molecular dissociation of tissue components to yield lowmolecular weight ablation by-products.

[0023] By the term “return electrode” is meant an electrode which servesto provide a current flow path from an active electrode back to a powersupply, and/or an electrode of an electrosurgical device which does notproduce an electrically-induced tissue-altering effect on tissuetargeted for treatment. By the term “active electrode” is meant anelectrode of an electrosurgical device which is adapted for producing anelectrically-induced tissue-altering effect when brought into contactwith, or close proximity to, a tissue targeted for treatment.

[0024] In another aspect, the invention provides an apparatus and methodfor treating tissue at a target site with an electrosurgical systemhaving a probe including an ablation electrode and a digestionelectrode, wherein the electrosurgical system lacks a dedicated returnelectrode. The ablation electrode and the digestion electrode areindependently coupled to opposite poles of a power supply for supplyingpower to the ablation electrode and to the digestion electrode.Typically, during operation of the electrosurgical system of theinvention the power supply does not supply power equally to the ablationelectrode and to the digestion electrode. Instead, at a given time pointduring operation of the electrosurgical system, one of the two electrodetypes (the ablation electrode(s) or the digestion electrode(s)) mayreceive up to about 100% of the available power from the power supply.

[0025] In a bipolar system with active and return electrodes havingcomparable dimensions (exposed surface ratio from 0.5 to 2.0), plasmaformation occurs on the electrode having the highest current density.The current density is influenced by field enhancement features such assharp edges, points, etc. The energy of the plasma is also defined bypotential gradient across the gaseous plasma, expressed in Volt/cm. Whenan electrode is placed at close proximity to tissue, the thickness ofthe gaseous bubble decreases, and therefore the voltage gradientincrease. This situation provides a stronger electrical field whichfavors plasma formation. When total active and return electrodes are ofcomparable surface area, plasma tends to form on the electrode that isin close proximity to tissue. Therefore, it is desirable to configurecertain electrodes to be more conducive to forming the plasma field(e.g., the ablation and/or digestion electrodes).

[0026] Shifting location of the ablative plasma from the ablationelectrode to the digestion electrode, and vice versa, may be effected bythe presence or absence of tissue (including whole tissue and resectedtissue fragments) in contact with, or in the vicinity of, the ablationand digestion electrodes. For example, when only the ablation electrodeis in contact with tissue (i.e., the digestion electrode is not incontact with tissue): a) plasma forms on the ablation electrode and theablation electrode functions as an active electrode (i.e., ablatestissue); and b) the electrical field at the digestion electrodedecreases, and the digestion electrode functions as a return electrode(i.e., has no tissue effect, and completes a current flow path from theablation electrode back to the power supply). Conversely, when only thedigestion electrode is in contact with tissue (i.e., the ablationelectrode is not in contact with tissue):

[0027] a) plasma forms at the digestion electrode, and the digestionelectrode functions as an active electrode; and b) the electrical fieldat the ablation electrode decreases, and the ablation electrodefunctions as a return electrode (i.e., has no tissue effect, andcompletes a current flow path from the digestion electrode back to thepower supply).

[0028] Thus, according to certain aspects of the invention, there isprovided an electrosurgical probe having a first electrode type and asecond electrode type, wherein both the first and second electrode typesare capable of serving as an active electrode and are adapted forablating tissue, and both the first and second electrode type arecapable of serving as a return electrode. The probe is designed tooperate in different modes according to whether i) only the firstelectrode type is in contact with tissue, ii) only the second electrodetype is in contact with tissue, or iii) both the first electrode typeand the second electrode type are in contact with tissue at the sametime. Typically, the electrosurgical probe is configured such that afirst electrode type can be brought into contact with tissue at a targetsite while a second electrode type does not contact the tissue at thetarget site. Indeed, in some embodiments the electrosurgical probe isconfigured such that one type of electrode can be brought into contactwith tissue at a target site while the other electrode type remainsremote from the tissue at the target site.

[0029] In one mode of operation, both the first electrode type (ablationelectrode) and second electrode type (digestion electrode) may be incontact with tissue simultaneously. Under these circumstances, byarranging for an appropriate ablation electrode:digestion electrodesurface area ratio and electrode geometry, the plasma may be formedpreferentially on the digestion electrode. When tissue is in contactwith, or in the vicinity of, the digestion electrode, the electricalimpedance in the vicinity of the digestion electrode changes. Such achange in electrical field typically results from the presence of one ormore tissue fragments flowing towards the digestion electrode in anaspiration stream comprising an electrically conductive fluid, and thechange in electrical impedance may trigger a shift from the ablationelectrode serving as active electrode to the digestion electrode servingas active electrode. The ablation electrode may be located distal to anaspiration port on the shaft. The digestion electrode may be arranged inrelation to an aspiration device, so that the aspiration stream contactsthe digestion electrode.

[0030] In another aspect, the present invention provides anelectrosurgical suction apparatus adapted for coupling to a highfrequency power supply and for removing tissue from a target site to betreated. The apparatus includes an aspiration channel terminating in adistal opening or aspiration port, and a plurality of active electrodesin the vicinity of the distal opening. The plurality of activeelectrodes may be structurally similar or dissimilar. In one embodiment,a plurality of active electrodes are arranged substantially parallel toeach other on an electrode support, and each of the plurality of activeelectrodes traverses a void in the electrode support.

[0031] Typically, each of the plurality of active electrodes includes afirst free end, a second connected end, and a loop portion having adistal face, the loop portion extending from a treatment surface of theelectrode support and spanning the aspiration port. In one embodiment,the orientation of an active electrode with respect to the treatmentsurface may change from a first direction in the region of the connectedend to a second direction in the region of the loop portion.

[0032] According to another aspect of the invention, the loop portion ofeach of the plurality of active electrodes may be oriented in aplurality of different directions with respect to the treatment surface.In one embodiment, the loop portion of each of the plurality of activeelectrodes is oriented in a different direction with respect to thetreatment surface. In one embodiment, the orthogonal distance from thetreatment surface to the distal face of each active electrode issubstantially the same.

[0033] According to one aspect of the invention, a baffle or screen isprovided at the distal end of the apparatus. In one embodiment thebaffle is recessed within the void to impede the flow of solid materialinto the aspiration channel, and to trap the solid material in thevicinity of at least one of the plurality of active electrodes, wherebythe trapped material may be readily digested.

[0034] In use, the plurality of active electrodes are coupled to a firstpole of the high frequency power supply, and a return electrode iscoupled to a second pole of the high frequency power supply forsupplying high frequency alternating current to the device. Each of theplurality of active electrodes is capable of ablating tissue via acontrolled ablation mechanism involving molecular dissociation of tissuecomponents to yield low molecular weight ablation by-products. Duringthis process, tissue fragments may be resected from the target site.Such resected tissue fragments may be digested by one or more of theplurality of active electrodes via essentially the same cool ablationmechanism as described above (i.e., involving molecular dissociation oftissue components), to form smaller tissue fragments and/or lowmolecular weight ablation by-products. The smaller tissue fragments andlow molecular weight ablation by-products, together with any otherunwanted materials (e.g., bodily fluids, extraneous saline) may beaspirated from the target site via the aspiration channel.

[0035] In another aspect, the present invention provides a method forremoving tissue from a target site via an electrosurgical suctiondevice, wherein the plurality of active electrodes are juxtaposed withthe target tissue, and a high frequency voltage is applied to theplurality of active electrodes sufficient to ablate the tissue vialocalized molecular dissociation of tissue components. The apparatus isadapted for efficiently ablating tissue and for rapidly removingunwanted materials, including resected tissue fragments, from the targetsite. The apparatus is further adapted for providing a relativelysmooth, even contour to a treated tissue.

[0036] According to another aspect of the invention, there is providedan electrosurgical probe having an aspiration unit including a pluralityof aspiration ports, a plurality of active electrodes, and a workingportion arranged at the distal end of the probe, wherein the workingportion includes a plurality of working zones. The plurality of activeelectrodes are disposed on an electrically insulating electrode support.The working zones may be spaced from each other, either axially orlaterally, on the electrode support. The working zones may bedistinguished from each other by their ablation rate and/or theiraspiration rate. Typically, each working zone has at least oneaspiration port and at least one active electrode. Each active electrodeis capable of generating a plasma, in the presence of an electricallyconductive fluid, and upon the application of a high frequency voltagebetween that active electrode and a return electrode. The returnelectrode may be disposed on the shaft distal end, at a locationproximal or inferior to the electrode support. Generally, a working zonehaving a relatively high aspiration rate has a relatively low ablationrate, and vice versa. In general, a working zone having a relativelyhigh aspiration rate is less suited to the initiation and maintenance ofa plasma, as compared with a working zone having a relatively lowaspiration rate.

[0037] In one embodiment, all of a plurality of working zones arearranged on a single plane of an electrode support. In anotherembodiment, the electrode support includes a plurality of planes, and aworking portion of the probe occupies at least two of the plurality ofplanes. In another embodiment, each of a plurality of working zonesoccupies a different plane of the electrode support. According to oneaspect of the invention, one or more of the active electrodes is in theform of a wire loop. The active electrodes may be strategically arrangedwith respect to the aspiration ports. In one embodiment, an electrodeloop at least partially extends across (traverses) one or moreaspiration ports. In another embodiment, at least a portion of theaspiration ports is located towards the periphery of a working zone ofthe electrode support.

[0038] According to another aspect of the invention, there is providedan electrosurgical probe having a first working zone and a secondworking zone, wherein the first working zone has a relatively lowaspiration rate and is adapted for aggressively ablating tissue from atarget site. In contrast, the second working zone includes at least oneaspiration port, has a relatively high aspiration rate, and is adaptedfor rapidly aspirating fluids therefrom. The second working zone has arelatively low ablation rate, which is, nevertheless, sufficient tovaporize tissue fragments resected by the first working zone, wherebyblockage of the at least one aspiration port of the second working zoneis avoided. In one aspect of the invention, the relative ablation rateof the first and second working zones can be “tuned” by the appropriateselection of the number, size, and distribution of aspiration ports foreach zone.

[0039] In another embodiment, there is provided a method for ablating atarget tissue using an electrosurgical probe having a working portionwhich includes a plurality of working zones. Each of the plurality ofworking zones may differ with respect to one or more of the followingcharacteristics: axial placement on the probe, number and/or size ofaspiration ports, aspiration rate, propensity to initiate and maintain aplasma, and ablation rate. The method involves advancing the probedistal end towards the target tissue, such that at least a first workingzone is in at least close proximity to the target tissue. Thereafter, ahigh frequency voltage is applied between at least one active electrodeof the working portion and a return electrode, whereby at least aportion of the target tissue is ablated. Typically, the ablation oftarget tissue in this manner occurs via plasma-induced moleculardissociation of target tissue components to produce low molecular weightor gaseous ablation by-products. In one embodiment, at least a portionof the ablation by-products are aspirated from the surgical site via oneor more aspiration ports located on a second working zone of the probe.The ablation of target tissue by the first working zone may result inthe resection of fragments of the target tissue. Such resected tissuefragments may be ablated (vaporized) by one or more active electrodes ofthe second working zone to once again form low molecular weight ablationby-products, whereby blockage of the aspiration ports is prevented.

[0040] According to another aspect, the invention provides anelectrosurgical probe including an active electrode assembly having anactive electrode screen disposed on a treatment surface of anelectrically insulating electrode support, and at least one activeelectrode terminal protruding from the treatment surface. The electrodesupport includes a suction cavity in communication with an aspirationport located within the treatment surface. The aspiration port and thesuction cavity represent a distal portion of an aspiration unit by whichmaterials, such as ablation by-products, may be conveniently removedfrom a surgical site during use of the probe.

[0041] Typically, the probe further includes a shaft, the activeelectrode assembly disposed at the shaft distal end, and a handleaffixed to the shaft proximal end, the handle housing a connectionblock. In one embodiment, the shaft comprises a metal tube having aproximal portion encased within an electrically insulating sleeve, andan exposed distal portion comprising a return electrode. The connectionblock is adapted for coupling the active electrode terminal(s), theactive electrode screen, and the return electrode to a high frequencypower supply.

[0042] In another embodiment, the invention provides an active electrodeassembly for an electrosurgical probe, the active electrode assemblyincluding an electrically insulating electrode support having atreatment surface, and at least one flow protector protruding from thetreatment surface. In one embodiment, each flow protector is in the formof a pillar or post extending substantially orthogonal to the treatmentsurface. The active electrode assembly further includes an activeelectrode screen disposed on the treatment surface. The active electrodeassembly still further includes a plurality of active electrodeterminals protruding from the treatment surface. A void within thetreatment surface defines an aspiration port, the aspiration port incommunication with a vacuum source. The active electrode screen includesa central portion substantially aligned with the aspiration port, thecentral portion having at least one screen void therein. Each flowprotector defines a shielded region of the active electrode screen, eachshielded region is characterized by a relatively low flow rate of anaspiration stream over an exposed surface of the active electrodescreen. Each shielded region promotes plasma formation by the activeelectrode screen upon application of a suitable high frequency voltagethereto. The active electrode screen is adapted for removing tissue froma surgical site and for digesting tissue fragments resected from thesurgical site.

[0043] According to another embodiment of the invention, there isprovided an active electrode screen comprising a metal plate having atleast one screen void therein and at least one wire lead coupled to themetal plate. In one embodiment, the plate and/or the wire lead(s)comprise a platinum/iridium alloy. Typically, the plate includes firstand second ends, first and second arms, and a central portion having aplurality of screen voids therein. In one embodiment, at least some ofthe screen voids have a diamond-like shape. Typically, the metal platehas a plurality of sharp edges and/or pointed projections. The sharpedges and pointed projections of the metal plate promote the generationand maintenance of a plasma upon application of a suitable highfrequency voltage to the active electrode screen.

[0044] In another embodiment, the invention provides a method forablating a target tissue at a surgical site, wherein the method involvespositioning an active electrode assembly of an electrosurgical probe inat least close proximity to the target tissue. The active electrodeassembly includes an active electrode screen disposed on a treatmentsurface of an electrically insulating electrode support, and a pluralityof active electrode terminals. A high frequency voltage is appliedbetween the active electrode terminal and a return electrode, andbetween the active electrode screen and the return electrode, whereinthe high frequency voltage is sufficient to ablate, or otherwise modifythe target tissue. In some embodiments, the method further involvesdelivering an electrically conductive fluid to the active electrodeassembly during application of the high frequency voltage. The electrodesupport includes a plurality of electrically insulating flow protectorsprotruding from the treatment surface. The flow protectors promoteinitiation and maintenance of a plasma by the active electrode screenupon application of the high frequency voltage. The method still furtherinvolves aspirating unwanted materials (such as gaseous ablationby-products, and the like) from the surgical site. In one embodiment,such unwanted materials are removed from the surgical site in anaspiration stream running from the treatment surface of the electrodesupport, through a suction cavity within the electrode support, to aproximal aspiration lumen. The aspiration lumen may be coupled to anaspiration tube, and the aspiration tube may, in turn, be coupled to asuitable vacuum source.

[0045] A further understanding of the nature and advantages of theinvention will become apparent by reference to the remaining portions ofthe specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0046]FIG. 1 is a perspective view of an electrosurgical systemincorporating a power supply and an electrosurgical probe for tissueablation, resection, incision, contraction and for vessel hemostasisaccording to the present invention;

[0047]FIG. 2 is a side view of an electrosurgical probe according to thepresent invention incorporating a loop electrode for resection andablation of tissue;

[0048]FIG. 3 is a cross-sectional view of the electrosurgical probe ofFIG. 2;

[0049]FIG. 4 is an exploded sectional view of a distal portion of theelectrosurgical probe;

[0050]FIGS. 5A and 5B are end and cross-sectional views, respectively,of the proximal portion of the probe;

[0051]FIG. 6 illustrates a surgical kit for removing and ablating tissueaccording to the present invention;

[0052]FIG. 7 is a perspective view of another electrosurgical systemincorporating a power supply, an electrosurgical probe and a supply ofelectrically conductive fluid for delivering the fluid to the targetsite;

[0053]FIG. 8 is a side view of another electrosurgical probe accordingto the present invention incorporating aspiration electrodes forablating aspirated tissue fragments and/or tissue strands, such assynovial tissue;

[0054]FIG. 9 is an end view of the probe of FIG. 8;

[0055]FIG. 10 is an exploded view of a proximal portion of theelectrosurgical probe;

[0056] FIGS. 11-13 illustrate alternative probes according to thepresent invention, incorporating aspiration electrodes;

[0057]FIG. 14 illustrates an endoscopic sinus surgery procedure, whereinan endoscope is delivered through a nasal passage to view a surgicalsite within the nasal cavity of the patient;

[0058]FIG. 15 illustrates an endoscopic sinus surgery procedure with oneof the probes described above according to the present invention;

[0059]FIGS. 16A and 16B illustrate a detailed view of the sinus surgeryprocedure, illustrating ablation of tissue according to the presentinvention;

[0060]FIG. 17 illustrates a procedure for treating obstructive sleepdisorders, such as sleep apnea, according to the present invention;

[0061]FIG. 18 is a perspective view of another embodiment of the presentinvention;

[0062]FIG. 19 is a side-cross-sectional view of the electrosurgicalprobe of FIG. 18;

[0063]FIG. 20 is an enlarged detailed cross-sectional view of the distalend portion of the probe of FIG. 18;

[0064]FIGS. 21 and 22 show the proximal end and the distal end,respectively, of the probe of FIG. 18;

[0065]FIG. 23 illustrates a method for removing fatty tissue from theabdomen, groin or thigh region of a patient according to the presentinvention;

[0066]FIG. 24 illustrates a method for removing fatty tissue in the headand neck region of a patient according to the present invention.

[0067]FIG. 25 is a perspective view of yet another embodiment of thepresent invention;

[0068]FIG. 26 is a side cross-sectional view of the electrosurgicalprobe of FIG. 25;

[0069]FIG. 27 is an enlarged detailed view of the distal end portion ofthe probe of FIG. 25;

[0070]FIG. 28 is a perspective view of the distal portion of the probeof FIG. 25;

[0071]FIG. 29 is a perspective view of an electrode support member ofthe probe of FIG. 25;

[0072]FIG. 30 illustrates the proximal end of the probe of FIG. 25; and

[0073]FIG. 31 is an alternative embodiment of the active electrode forthe probe of FIG. 25;

[0074]FIG. 32 shows an electrosurgical probe including a resection unit,according to another embodiment of the invention;

[0075]FIG. 33 shows a resection unit of an electrosurgical probe, theresection unit including a resection electrode on a resection electrodesupport;

[0076] FIGS. 34A-D each show an electrosurgical probe including aresection unit, according to various embodiments of the invention;

[0077]FIG. 35A shows an electrosurgical probe including a resection unitand an aspiration device, according to the invention;

[0078]FIG. 35B shows an electrosurgical probe including a resection unitand a fluid delivery device, according to one embodiment of theinvention;

[0079] FIGS. 36A-F each show a resection unit having at least oneresection electrode head arranged on a resection electrode support,according to various embodiments of the invention;

[0080]FIG. 37 illustrates an arrangement of a resection electrode headwith respect to the longitudinal axis of a resection unit;

[0081]FIG. 38A shows, in plan view, a resection electrode supportdisposed on a shaft distal end of an electrosurgical probe;

[0082] FIGS. 38B-D each show a profile of a resection electrode head ona resection electrode support;

[0083] FIGS. 39A-I each show a cross-section of a resection electrodehead, according to one embodiment of the invention, as seen along thelines 39A-I of FIG. 38B;

[0084]FIG. 40 shows a cross-section of a resection electrode head havingan exposed cutting edge and a covered portion having an insulatinglayer, according to another embodiment of the invention;

[0085]FIG. 41A illustrates a distal end of an electrosurgical probeincluding a plurality of resection electrode heads, according to anotherembodiment of the invention;

[0086]FIG. 41B illustrates the distal end of the electrosurgical probeof FIG. 41A taken along the lines 41B-41B;

[0087]FIG. 41C illustrates the distal end of the electrosurgical probeof FIG. 41A taken along the lines 41C-41C;

[0088]FIG. 42A is a sectional view of a distal end portion of anelectrosurgical shaft, according to one embodiment of the invention;

[0089]FIG. 42B illustrates the distal end of the shaft of FIG. 42A takenalong the lines 42B-42B;

[0090] FIGS. 43A-D are side views of the shaft distal end portion of anelectrosurgical probe, according to another embodiment of the invention;

[0091] FIGS. 44A-D each show a resection unit in relation to a fluiddelivery device, according to various embodiments of the invention;

[0092]FIG. 45 shows a shaft distal end portion of an electrosurgicalprobe, according to one embodiment of the invention;

[0093]FIG. 46 schematically represents a surgical kit for resection andablation of tissue, according to another embodiment of the invention;

[0094] FIGS. 47A-B schematically represent a method of performing aresection and ablation electrosurgical procedure, according to anotherembodiment of the invention;

[0095]FIG. 48 schematically represents a method of making a resectionand ablation electrosurgical probe, according to yet another embodimentof the invention;

[0096]FIG. 49 is a side view of an electrosurgical probe havingelectrodes mounted on the distal terminus of the probe shaft, accordingto one embodiment of the invention;

[0097]FIG. 50A shows a longitudinal section of a probe showing detail ofthe shaft and handle;

[0098]FIG. 50B is an end view of the distal terminus of theelectrosurgical probe of FIG. 50A;

[0099]FIG. 51A shows a longitudinal section of a probe showing detail ofthe shaft distal end, according to another embodiment of the invention;

[0100]FIG. 51B is an end view of the distal terminus of theelectrosurgical probe of FIG. 51A;

[0101]FIG. 52A shows a longitudinal section of a probe showing detail ofthe shaft distal end, according to another embodiment of the invention;

[0102]FIG. 52B is an end view of the distal terminus of theelectrosurgical probe of FIG. 52A;

[0103] FIGS. 53A-D show side, perspective, face, and sectional views,respectively of an electrode support of an electrosurgical probe,according to another embodiment of the invention;

[0104]FIGS. 54 and 55 each show a sectional view of an electrode supportof an electrosurgical probe, according to two different embodiments ofthe invention;

[0105]FIG. 56A shows a longitudinal section of the shaft distal end ofan electrosurgical probe, according to another embodiment of theinvention;

[0106]FIG. 56B is an end view of the distal terminus of theelectrosurgical probe of FIG. 56A;

[0107]FIG. 56C shows attachment of an ablation electrode to an electrodesupport;

[0108]FIG. 57A shows a longitudinal section of the shaft distal end ofan electrosurgical probe, according to another embodiment of theinvention;

[0109]FIG. 57B is an end view of the distal terminus of theelectrosurgical probe of FIG. 57A;

[0110]FIG. 58 is a perspective view of a digestion electrode of anelectrosurgical probe, according to one embodiment of the invention;

[0111]FIG. 59A shows a longitudinal section view of the shaft distal endof an electrosurgical probe, having an electrode mounted laterally onthe shaft distal end, according to another embodiment of the invention;

[0112]FIG. 59B is a plan view of the shaft distal end shown in FIG. 59A;

[0113]FIG. 60A shows a plan view of the shaft distal end of anelectrosurgical probe, having ablation and digestion electrodes mountedlaterally on the shaft distal end, according to another embodiment ofthe invention;

[0114]FIG. 60B shows a transverse cross-section of the shaft distal endof FIG. 60A;

[0115]FIG. 61 schematically represents a series of steps involved in amethod of aggressively removing tissue during a surgical procedure;

[0116]FIGS. 62A and 62B show a side view and an end-view, respectively,of an electrosurgical suction apparatus, according to another embodimentof the invention;

[0117]FIG. 62C shows a longitudinal cross-section of the apparatus ofFIGS. 62A, 62B;

[0118]FIG. 63A shows a longitudinal cross-section of the shaft distalend of an electrosurgical suction apparatus, according to the invention;

[0119]FIG. 63B shows a transverse cross-sectional view of an activeelectrode of the apparatus of FIG. 63A as taken along the lines 63B-63B;

[0120]FIG. 63C shows an active electrode in communication with anelectrode lead;

[0121]FIG. 64A shows an electrosurgical suction apparatus having anouter sheath, according to another embodiment of the invention;

[0122]FIG. 64B shows a transverse cross-section of the apparatus of FIG.64A;

[0123]FIG. 65A shows a longitudinal cross-section of the shaft distalend of an electrosurgical suction apparatus having a baffle, and FIG.65B is an end view of the apparatus of FIG. 65A, according to anotherembodiment of the invention;

[0124]FIGS. 66A and 66B each show a longitudinal cross-section of theshaft distal end of an electrosurgical suction apparatus, according totwo different embodiments of the invention;

[0125]FIGS. 67A and 67B show a perspective view and a side view,respectively, of the shaft distal end of an electrosurgical suctionapparatus, according to another embodiment of the invention;

[0126]FIG. 68A is a block diagram representing an electrosurgicalsystem, according to another embodiment of the invention;

[0127]FIG. 68B is a block diagram representing an electrosurgical probeof the system of FIG. 68A,

[0128] FIGS. 69A-69C each schematically represent a working portion ofan electrosurgical probe, according to various embodiments of theinvention;

[0129]FIG. 70A is a longitudinal sectional view of an electrosurgicalprobe, according to one embodiment of the invention;

[0130]FIG. 70B is a perspective view of the distal portion of theelectrosurgical probe of FIG. 70A;

[0131]FIG. 71A is a perspective view of the distal portion of anelectrosurgical probe, according to another embodiment of the invention;

[0132]FIG. 71B is a side view of the distal portion of the probe of FIG.71A;

[0133]FIG. 72 is a perspective view of the distal portion of anelectrosurgical probe, according to another embodiment of the invention;

[0134]FIG. 73A is a perspective view of the distal portion of anelectrosurgical probe, according to another embodiment of the invention;

[0135]FIG. 72B is a plan view of the distal portion of the probe of FIG.73A;

[0136]FIG. 74 schematically represents a series of steps involved in amethod of ablating tissue, according to another embodiment of theinvention;

[0137] FIGS. 75A-D are block diagrams schematically representingelectrosurgical apparatus, according to another embodiment of theinvention;

[0138] FIGS. 76A-B show a perspective view and an end view,respectively, of an electrode support having a plurality of flowprotectors, according to one embodiment of the invention;

[0139] FIGS. 77A-C show an active electrode assembly including aplurality of flow protectors, according to the invention;

[0140]FIG. 78 schematically represents an active electrode screen, inplan view, showing the location of two shielded regions of the screen inrelation to two flow protectors, according to one embodiment of theinvention;

[0141]FIG. 79 schematically represents an electrosurgical probe,according to one embodiment of the invention;

[0142] FIGS. 80A-B show a side view and a perspective view,respectively, of an active electrode screen, according to one embodimentof the invention; and

[0143]FIG. 81 schematically represents a series of steps involved in amethod of ablating tissue, according to another embodiment of theinvention.

DESCRIPTION OF SPECIFIC EMBODIMENTS

[0144] The present invention provides systems and methods forselectively applying electrical energy to a target location within or ona patient's body. The present invention is particularly useful inprocedures where the tissue site is flooded or submerged with anelectrically conductive fluid, such as arthroscopic surgery of the knee,shoulder, ankle, hip, elbow, hand or foot. In addition, tissues whichmay be treated by the system and method of the present inventioninclude, but are not limited to, prostate tissue and leiomyomas(fibroids) located within the uterus, gingival tissues and mucosaltissues located in the mouth, tumors, scar tissue, myocardial tissue,collagenous tissue within the eye or epidermal and dermal tissues on thesurface of the skin. Other procedures for which the present inventionmay be used include laminectomy/disketomy procedures for treatingherniated disks, decompressive laminectomy for stenosis in thelumbosacral and cervical spine, posterior lumbosacral and cervical spinefusions, treatment of scoliosis associated with vertebral disease,foraminotomies to remove the roof of the intervertebral foramina torelieve nerve root compression, as well as anterior cervical and lumbardiskectomies. The present invention is also useful for resecting tissuewithin accessible sites of the body that are suitable for electrode loopresection, such as the resection of prostate tissue, leiomyomas(fibroids) located within the uterus, and other diseased tissue withinthe body.

[0145] The present invention is also useful for procedures in the headand neck, such as the ear, mouth, pharynx, larynx, esophagus, nasalcavity and sinuses. These procedures may be performed through the mouthor nose using speculae or gags, or using endoscopic techniques, such asfunctional endoscopic sinus surgery (FESS). These procedures may includethe removal of swollen tissue, chronically-diseased inflamed andhypertrophic mucus linings, polyps and/or neoplasms from the variousanatomical sinuses of the skull, the turbinates and nasal passages, inthe tonsil, adenoid, epi-glottic and supra-glottic regions, and salivaryglands, submucous resection of the nasal septum, excision of diseasedtissue and the like. In other procedures, the present invention may beuseful for collagen shrinkage, ablation and/or hemostasis in proceduresfor treating snoring and obstructive sleep apnea (e.g., soft palate,such as the uvula, or tongue/pharynx stiffening, and midlineglossectomies), for gross tissue removal, such as tonsillectomies,adenoidectomies, tracheal stenosis and vocal cord polyps and lesions, orfor the resection or ablation of facial tumors or tumors within themouth and pharynx, such as glossectomies, laryngectomies, acousticneuroma procedures and nasal ablation procedures. In addition, thepresent invention is useful for procedures within the ear, such asstapedotomies, tympanostomies, or the like.

[0146] The present invention may also be useful for cosmetic and plasticsurgery procedures in the head and neck. For example, the presentinvention is particularly useful for ablation and sculpting of cartilagetissue, such as the cartilage within the nose that is sculpted duringrhinoplasty procedures. The present invention may also be employed forskin tissue removal and/or collagen shrinkage in the epidermis or dermistissue in the head and neck, e.g., the removal of pigmentations,vascular lesions (e.g., leg veins), scars, tattoos, etc., and for othersurgical procedures on the skin, such as tissue rejuvenation, cosmeticeye procedures (blepharoplasties), wrinkle removal, tightening musclesfor facelifts or browlifts, hair removal and/or transplant procedures,etc.

[0147] For convenience, certain embodiments of the invention will bedescribed primarily with respect to the resection and/or ablation of themeniscus and the synovial tissue within a joint during an arthroscopicprocedure and to the ablation, resection and/or aspiration of sinustissue during an endoscopic sinus surgery procedure, but it will beappreciated that the systems and methods can be applied equally well toprocedures involving other tissues of the body, as well as to otherprocedures including open procedures, intravascular procedures, urology,laparoscopy, arthroscopy, thoracoscopy or other cardiac procedures,dermatology, orthopedics, gynecology, otorhinolaryngology, spinal andneurologic procedures, oncology, and the like.

[0148] In the present invention, high frequency (RF) electrical energyis applied to one or more active electrodes in the presence ofelectrically conductive fluid to remove and/or modify the structure oftissue structures. Depending on the specific procedure, the presentinvention may be used to: (1) volumetrically remove tissue, bone orcartilage (i.e., ablate or effect molecular dissociation of the tissuestructure); (2) cut or resect tissue; (3) shrink or contract collagenconnective tissue; and/or (4) coagulate severed blood vessels.

[0149] In one aspect of the invention, systems and methods are providedfor the volumetric removal or ablation of tissue structures. In theseprocedures, a high frequency voltage difference is applied between oneor more active electrode(s) and one or more return electrode(s) todevelop high electric field intensities in the vicinity of the targettissue site. The high electric field intensities lead to electric fieldinduced molecular breakdown of target tissue through moleculardissociation (rather than thermal evaporation or carbonization).Applicant believes that the tissue structure is volumetrically removedthrough molecular disintegration of larger organic molecules intosmaller molecules and/or atoms, such as hydrogen, oxides of carbon,hydrocarbons and nitrogen compounds. This molecular disintegrationcompletely removes the tissue structure, as opposed to dehydrating thetissue material by the removal of liquid from within the cells of thetissue, as is typically the case with electrosurgical desiccation andvaporization.

[0150] The high electric field intensities may be generated by applyinga high frequency voltage that is sufficient to vaporize an electricallyconductive fluid over at least a portion of the active electrode(s) inthe region between the distal tip of the active electrode(s) and thetarget tissue. The electrically conductive fluid may be a gas or liquid,such as isotonic saline, delivered to the target site, or a viscousfluid, such as a gel, that is located at the target site. In the latterembodiment, the active electrode(s) are submersed in the electricallyconductive gel during the surgical procedure. Since the vapor layer orvaporized region has a relatively high electrical impedance, itminimizes the current flow into the electrically conductive fluid. Thisionization, under optimal conditions, induces the discharge of energeticelectrons and photons from the vapor layer to the surface of the targettissue. A more detailed description of this cold ablation phenomenon,termed Coblation®, can be found in commonly assigned U.S. Pat. No.5,683,366 the complete disclosure of which is incorporated herein byreference.

[0151] The present invention applies high frequency (RF) electricalenergy in an electrically conductive fluid environment to remove (i.e.,resect, cut, or ablate) or contract a tissue structure, and to sealtransected vessels within the region of the target tissue. The presentinvention is particularly useful for sealing larger arterial vessels,e.g., on the order of 1 mm in diameter or greater. In some embodiments,a high frequency power supply is provided having an ablation mode,wherein a first voltage is applied to an active electrode sufficient toeffect molecular dissociation or disintegration of the tissue, and acoagulation mode, wherein a second, lower voltage is applied to anactive electrode (either the same or a different electrode) sufficientto achieve hemostasis of severed vessels within the tissue. In otherembodiments, an electrosurgical probe is provided having one or morecoagulation electrode(s) configured for sealing a severed vessel, suchas an arterial vessel, and one or more active electrodes configured foreither contracting the collagen fibers within the tissue or removing(ablating) the tissue, e.g., by applying sufficient energy to the tissueto effect molecular dissociation. In the latter embodiments, thecoagulation electrode(s) may be configured such that a single voltagecan be applied to coagulate tissue with the coagulation electrode(s),and to ablate or contract the tissue with the active electrode(s). Inother embodiments, the power supply is combined with the probe such thatthe coagulation electrode receives power when the power supply is in thecoagulation mode (low voltage), and the active electrode(s) receivepower when the power supply is in the ablation mode (higher voltage).

[0152] In the method of the present invention, one or more activeelectrodes are brought into close proximity to tissue at a target site,and the power supply is activated in the ablation mode such thatsufficient voltage is applied between the active electrodes and thereturn electrode to volumetrically remove the tissue through moleculardissociation, as described below. During this process, vessels withinthe tissue will be severed. Smaller vessels will be automatically sealedwith the system and method of the present invention. Larger vessels, andthose with a higher flow rate, such as arterial vessels, may not beautomatically sealed in the ablation mode. In these cases, the severedvessels may be sealed by activating a control (e.g., a foot pedal) toreduce the voltage of the power supply and to convert the system intothe coagulation mode. In this mode, the active electrodes may be pressedagainst the severed vessel to provide sealing and/or coagulation of thevessel. Alternatively, a coagulation electrode located on the same or adifferent probe may be pressed against the severed vessel. Once thevessel is adequately sealed, the surgeon activates a control (e.g.,another foot pedal) to increase the voltage of the power supply andconvert the system back into the ablation mode.

[0153] The present invention is particularly useful for removing orablating tissue around nerves, such as spinal or cranial nerves, e.g.,the olfactory nerve on either side of the nasal cavity, the optic nervewithin the optic and cranial canals, and the palatine nerve within thenasal cavity, soft palate, uvula and tonsil, etc. One of the significantdrawbacks with prior art microdebriders and lasers is that these devicesdo not differentiate between the target tissue and the surroundingnerves or bone. Therefore, the surgeon must be extremely careful duringthese procedures to avoid damage to the bone or nerves within and aroundthe nasal cavity. In the present invention, the Coblation process forremoving tissue results in extremely small depths of collateral tissuedamage as discussed above. This allows the surgeon to remove tissueclose to a nerve without causing collateral damage to the nerve fibers.

[0154] In addition to the generally precise nature of the novelmechanisms of the present invention, applicant has discovered anadditional method of ensuring that adjacent nerves are not damagedduring tissue removal. According to the present invention, systems andmethods are provided for distinguishing between the fatty tissueimmediately surrounding nerve fibers and the normal tissue that is to beremoved during the procedure. Peripheral nerves usually comprise aconnective tissue sheath, or epineurium, enclosing the bundles of nervefibers to protect these nerve fibers. This protective tissue sheathtypically comprises a fatty tissue (e.g., adipose tissue) havingsubstantially different electrical properties than the normal targettissue, such as the turbinates, polyps, mucus tissue or the like, thatare, for example, removed from the nose during sinus procedures. Thesystem of the present invention measures the electrical properties ofthe tissue at the tip of the probe with one or more active electrode(s).These electrical properties may include electrical conductivity at one,several or a range of frequencies (e.g., in the range from 1 kHz to 100MHz), dielectric constant, capacitance or combinations of these. In thisembodiment, an audible signal may be produced when the sensingelectrode(s) at the tip of the probe detects the fatty tissuesurrounding a nerve, or direct feedback control can be provided to onlysupply power to the active electrode(s), either individually or to thecomplete array of electrodes, if and when the tissue encountered at thetip or working end of the probe is normal tissue based on the measuredelectrical properties.

[0155] In one embodiment, the current limiting elements (discussed indetail below) are configured such that the active electrodes will shutdown or turn off when the electrical impedance of tissue at the tip ofthe probe reaches a threshold level. When this threshold level is set tothe impedance of the fatty tissue surrounding nerves, the activeelectrodes will shut off whenever they come in contact with, or in closeproximity to, nerves. Meanwhile, the other active electrodes, which arein contact with or in close proximity to nasal tissue, will continue toconduct electric current to the return electrode. This selectiveablation or removal of lower impedance tissue in combination with theCoblation® mechanism of the present invention allows the surgeon toprecisely remove tissue around nerves or bone.

[0156] In addition to the above, applicant has discovered that theCoblation® mechanism of the present invention can be manipulated toablate or remove certain tissue structures, while having little effecton other tissue structures. As discussed above, the present inventionuses a technique of vaporizing electrically conductive fluid to form aplasma layer or pocket around the active electrode(s), and then inducingthe discharge of energy from this plasma or vapor layer to break themolecular bonds of the tissue structure. Based on initial experiments,applicants believe that the free electrons within the ionized vaporlayer are accelerated in the high electric fields near the electrodetip(s). When the density of the vapor layer (or within a bubble formedin the electrically conductive liquid) becomes sufficiently low (i.e.,less than approximately 10²⁰ atoms/cm³ for aqueous solutions), theelectron mean free path increases to enable subsequently injectedelectrons to cause impact ionization within these regions of low density(i.e., vapor layers or bubbles). Energy evolved by the energeticelectrons (e.g., 4 to 5 eV) can subsequently bombard a molecule andbreak its bonds, dissociating a molecule into free radicals, which thencombine to form gaseous or liquid Coblation® by-products.

[0157] The energy evolved by the energetic electrons may be varied byadjusting a variety of factors, such as: the number of activeelectrodes; electrode size and spacing; electrode surface area;asperities and sharp edges on the electrode surfaces; electrodematerials; applied voltage and power; current limiting means, such asinductors; electrical conductivity of the fluid in contact with theelectrodes; density of the fluid; and other factors. Accordingly, thesefactors can be manipulated to control the energy level of the excitedelectrons. Since different tissue structures have different molecularbonds, the present invention can be configured to break the molecularbonds of certain tissue, while having too low an energy to break themolecular bonds of other tissue. For example, components of adiposetissue have double bonds that require a substantially higher energylevel than 4 to 5 eV to break. Accordingly, the present invention in itscurrent configuration generally does not ablate or remove such fattytissue. However, the present invention may be used to effectively ablatecells to release the inner fat content in a liquid form. Of course,factors may be changed such that these double bonds can be broken (e.g.,increasing the voltage or changing the electrode configuration toincrease the current density at the electrode tips).

[0158] In another aspect of the invention, a loop electrode is employedto resect, shape or otherwise remove tissue fragments from the treatmentsite, and one or more active electrodes are employed to ablate (i.e.,break down the tissue by processes including molecular dissociation ordisintegration) the non-ablated tissue fragments in situ. Once a tissuefragment is cut, partially ablated or resected by the loop electrode,one or more active electrodes will be brought into close proximity tothese fragments (either by moving the probe into position, or by drawingthe fragments to the active electrodes with a suction lumen). Voltage isapplied between the active electrodes and the return electrode tovolumetrically remove the fragments through molecular dissociation, asdescribed above. The loop electrode and the active electrodes arepreferably electrically isolated from each other such that, for example,current can be limited (passively or actively) or completely interruptedto the loop electrode as the surgeon employs the active electrodes toablate tissue fragments (and vice versa).

[0159] In another aspect of the invention, the loop electrode(s) areemployed to ablate tissue using the Coblation® mechanisms describedabove. In these embodiments, the loop electrode(s) provides a relativelyuniform smooth cutting or ablation effect across the tissue. Inaddition, loop electrodes generally have a larger surface area exposedto electrically conductive fluid (as compared to the smaller activeelectrodes described above), which increases the rate of ablation oftissue. Preferably, the loop electrode(s) extend a sufficient distancefrom the electrode support member selected to achieve a desirableablation rate, while minimizing power dissipation into the surroundingmedium (which could cause undesirable thermal damage to surrounding orunderlying tissue). In an exemplary embodiment, the loop electrode has alength from one end to the other end of about 0.5 to 20 mm, usuallyabout 1 to 8 mm. The loop electrode usually extends about 0.25 to 10 mmfrom the distal end of the support member, preferably about 1 to 4 mm.

[0160] The loop electrode(s) may have a variety of cross-sectionalshapes. Electrode shapes according to the present invention can includethe use of formed wire (e.g., by drawing round wire through a shapingdie) to form electrodes with a variety of cross-sectional shapes, suchas square, rectangular, L or V shaped, or the like. Electrode edges mayalso be created by removing a portion of the elongate metal electrode toreshape the cross-section. For example, material can be removed alongthe length of a solid or hollow wire electrode to form D or C shapedwires, respectively, with edges facing in the cutting direction.Alternatively, material can be removed at closely spaced intervals alongthe electrode length to form transverse grooves, slots, threads or thelike along the electrodes.

[0161] In some embodiments, the loop electrode(s) will have a“non-active” portion or surface to selectively reduce undesirablecurrent flow from the non-active portion or surface into tissue orsurrounding electrically conductive liquids (e.g., isotonic saline,blood or blood/non-conducting irrigant mixtures). Preferably, the“non-active” electrode portion will be coated with an electricallyinsulating material. This can be accomplished, for example, with plasmadeposited coatings of an insulating material, thin-film deposition of aninsulating material using evaporative or sputtering techniques (e.g.,SiO₂ or Si₃N₄), dip coating, or by providing an electrically insulatingsupport member to electrically insulate a portion of the externalsurface of the electrode. The electrically insulated non-active portionof the active electrode(s) allows the surgeon to selectively resectand/or ablate tissue, while minimizing necrosis or ablation ofsurrounding non-target tissue or other body structures.

[0162] In addition, the loop electrode(s) may comprise a singleelectrode extending from first and second ends to an insulating supportin the shaft, or multiple, electrically isolated electrodes extendingaround the loop. One or more return electrodes may also be positionedalong the loop portion. Further descriptions of these configurations canbe found in U.S. application Ser. No. 08/687,792, filed on Jul. 18,1996, now U.S. Pat. No. 5,843,019, which as already been incorporatedherein by reference.

[0163] The electrosurgical probe will comprise a shaft or a handpiecehaving a proximal end and a distal end which supports one or more activeelectrode(s). The shaft or handpiece may assume a wide variety ofconfigurations, with the primary purpose being to mechanically supportthe active electrode and permit the treating physician to manipulate theelectrode from a proximal end of the shaft. The shaft may be rigid orflexible, with flexible shafts optionally being combined with agenerally rigid external tube for mechanical support. The distal portionof the shaft may comprise a flexible material, such as plastics,malleable stainless steel, etc, so that the physician can mold thedistal portion into different configurations for different applications.Flexible shafts may be combined with pull wires, shape memory actuators,and other known mechanisms for effecting selective deflection of thedistal end of the shaft to facilitate positioning of the electrodearray. The shaft will usually include a plurality of wires or otherconductive elements running axially therethrough to permit connection ofthe electrode array to a connector at the proximal end of the shaft.Thus, the shaft will typically have a length of at least 5 cm for oralprocedures and at least 10 cm, more typically being 20 cm, or longer forendoscopic procedures. The shaft will typically have a diameter of atleast 0.5 mm and frequently in the range of from about 1 to 10 mm. Ofcourse, for dermatological procedures on the outer skin, the shaft mayhave any suitable length and diameter that would facilitate handling bythe surgeon.

[0164] For procedures within the nose and joints, the shaft will have asuitable diameter and length to allow the surgeon to reach the target bydelivering the probe shaft through an percutaneous opening in thepatient (e.g., a portal formed in the joint in arthroscopic surgery, orthrough one of the patient's nasal passages in FESS). Thus, the shaftwill usually have a length in the range of from about 5 to 25 cm, and adiameter in the range of from about 0.5 to 5 mm. For proceduresrequiring the formation of a small hole or channel in tissue, such astreating swollen turbinates, the shaft diameter will usually be lessthan 3 mm, preferably less than about 1 mm. Likewise, for procedures inthe ear, the shaft should have a length in the range of about 3 to 20cm, and a diameter of about 0.3 to 5 mm. For procedures in the mouth orupper throat, the shaft will have any suitable length and diameter thatwould facilitate handling by the surgeon. For procedures in the lowerthroat, such as laryngectomies, the shaft will be suitably designed toaccess the larynx. For example, the shaft may be flexible, or have adistal bend to accommodate the bend in the patient's throat. In thisregard, the shaft may be a rigid shaft having a specifically designedbend to correspond with the geometry of the mouth and throat, or it mayhave a flexible distal end, or it may be part of a catheter. In any ofthese embodiments, the shaft may also be introduced through rigid orflexible endoscopes. Specific shaft designs will be described in detailin connection with the figures hereinafter.

[0165] The current flow path between the active electrode(s) and thereturn electrode(s) may be generated by submerging the tissue site in anelectrically conductive fluid (e.g., a viscous fluid, such as anelectrically conductive gel), or by directing an electrically conductivefluid along a fluid path to the target site (i.e., a liquid, such asisotonic saline, or a gas, such as argon). This latter method isparticularly effective in a dry environment (i.e., the tissue is notsubmerged in fluid) because the electrically conductive fluid provides asuitable current flow path from the active electrode to the returnelectrode. A more complete description of an exemplary method ofdirecting electrically ′conductive fluid between the active and returnelectrodes is described in parent application Ser. No. 08/485,219, filedJun. 7, 1995, now U.S. Pat. No. 5,697,281, previously incorporatedherein by reference.

[0166] In some procedures, it may also be necessary to retrieve oraspirate the electrically conductive fluid after it has been directed tothe target site. For example, in procedures in the nose, mouth orthroat, it may be desirable to aspirate the fluid so that it does notflow down the patient's throat. In addition, it may be desirable toaspirate small pieces of tissue that are not completely disintegrated bythe high frequency energy, air bubbles, or other fluids at the targetsite, such as blood, mucus, the gaseous products of ablation, etc.Accordingly, the system of the present invention can include a suctionlumen in the probe, or on another instrument, for aspirating fluids fromthe target site.

[0167] In some embodiments, the probe will include one or moreaspiration electrode(s) coupled to the distal end of the suction lumenfor ablating, or at least reducing the volume of, tissue fragments thatare aspirated into the lumen. The aspiration electrode(s) functionmainly to inhibit clogging of the lumen that may otherwise occur aslarger tissue fragments are drawn therein. The aspiration electrode(s)may be different from the ablation active electrode(s), or the sameelectrode(s) may serve both functions. In some embodiments, the probewill be designed to use suction force to draw loose tissue, such assynovial tissue to the aspiration or ablation electrode(s) on the probe,which are then energized to ablate the loose tissue.

[0168] In other embodiments, the aspiration lumen can be positionedproximal of the active electrodes a sufficient distance such that theaspiration lumen will primarily aspirate air bubbles and body fluidssuch as blood, mucus, or the like. Such a configuration allows theelectrically conductive fluid to dwell at the target site for a longerperiod. Consequently, the plasma can be created more aggressively at thetarget site and the tissue can be treated in a more efficient manner.Additionally, by positioning the aspiration lumen opening somewhatdistant from the active electrodes, it may not be necessary to haveablation electrodes at the lumen opening since, in this configuration,tissue fragments will typically not be aspirated through the lumen.

[0169] The present invention may use a single active electrode or anelectrode array distributed over a contact surface of a probe. In thelatter embodiment, the electrode array usually includes a plurality ofindependently current-limited and/or power-controlled active electrodesto apply electrical energy selectively to the target tissue whilelimiting the unwanted application of electrical energy to thesurrounding tissue and environment. Such unwanted application ofelectrical energy results from power dissipation into surroundingelectrically conductive liquids, such as blood, normal saline,electrically conductive gel and the like. The active electrodes may beindependently current-limited by isolating the terminals from each otherand connecting each terminal to a separate power source that is isolatedfrom the other active electrodes. Alternatively, the active electrodesmay be connected to each other at either the proximal or distal ends ofthe probe to form a single connector that couples to a power source.

[0170] In one configuration, each individual active electrode in theelectrode array is electrically insulated from all other activeelectrodes in the array within the probe and is connected to a powersource which is isolated from each of the other active electrodes in thearray or to circuitry which limits or interrupts current flow to theactive electrode when low resistivity material (e.g., blood,electrically conductive saline irrigant or electrically conductive gel)causes a lower impedance path between the return electrode and theindividual active electrode. The isolated power sources for eachindividual active electrode may be separate power supply circuits havinginternal impedance characteristics which limit power to the associatedactive electrode when a low impedance return path is encountered. By wayof example, the isolated power source may be a user selectable constantcurrent source. In this embodiment, lower impedance paths willautomatically result in lower resistive heating levels since the heatingis proportional to the square of the operating current times theimpedance. Alternatively, a single power source may be connected to eachof the active electrodes through independently actuatable switches, orby independent current limiting elements, such as inductors, capacitors,resistors and/or combinations thereof. The current limiting elements maybe provided in the probe, connectors, cable, controller or along theconductive path from the controller to the distal tip of the probe.Alternatively, the resistance and/or capacitance may occur on thesurface of the active electrode(s) due to oxide layers which formselected active electrodes (e.g., titanium or a resistive coating on thesurface of metal, such as platinum).

[0171] The tip region of the probe may comprise many independent activeelectrodes designed to deliver electrical energy in the vicinity of thetip. The selective application of electrical energy to the conductivefluid is achieved by connecting each individual active electrode and thereturn electrode to a power source having independently controlled orcurrent limited channels. The return electrode(s) may comprise a singletubular member of conductive material proximal to the electrode array atthe tip which also serves as a conduit for the supply of theelectrically conductive fluid between the active and return electrodes.Alternatively, the probe may comprise an array of return electrodes atthe distal tip of the probe (together with the active electrodes) tomaintain the electric current at the tip. The application of highfrequency voltage between the return electrode(s) and the electrodearray results in the generation of high electric field intensities atthe distal tips of the active electrodes with conduction of highfrequency current from each individual active electrode to the returnelectrode. The current flow from each individual active electrode to thereturn electrode(s) is controlled by either active or passive means, ora combination thereof, to deliver electrical energy to the surroundingconductive fluid while minimizing energy delivery to surrounding(non-target) tissue.

[0172] The application of a high frequency voltage between the returnelectrode(s) and the active electrode(s) for appropriate time intervalseffects cutting, removing, ablating, shaping, contracting or otherwisemodifying the target tissue. The tissue volume over which energy isdissipated (i.e., over which a high current density exists) may beprecisely controlled, for example, by the use of a multiplicity of smallactive electrodes whose effective diameters or principal dimensionsrange from about 5 mm to 0.01 mm, preferably from about 2 mm to 0.05 mm,and more preferably from about 1 mm to 0.1 mm. In these embodiments,electrode areas for both circular and non-circular terminals will have acontact area (per active electrode) below 25 mm², preferably being inthe range from 0.0001 mm² to 1 mm², and more preferably from 0.005 mm²to 0.5 mm². The circumscribed area of the electrode array is in therange from 0.25 mm² to 75 mm², preferably from 0.5 mm² to 40 mm², andwill usually include at least two isolated active electrodes, preferablyat least five active electrodes, often greater than 10 active electrodesand even 50 or more active electrodes, disposed over the distal contactsurfaces on the shaft. The use of small diameter active electrodesincreases the electric field intensity and reduces the extent or depthof tissue heating as a consequence of the divergence of current fluxlines which emanate from the exposed surface of each active electrode.

[0173] The area of the tissue treatment surface can vary widely, and thetissue treatment surface can assume a variety of geometries, withparticular areas and geometries being selected for specificapplications. Active electrode surfaces can have areas in the range from0.25 mm² to 75 mm², usually being from about 0.5 mm² to 40 mm². Thegeometries can be planar, concave, convex, hemispherical, conical,linear “in-line” array or virtually any other regular or irregularshape. Most commonly, the active electrode(s) or active electrode(s)will be formed at the distal tip of the electrosurgical probe shaft,frequently being planar, disk-shaped, or hemispherical surfaces for usein reshaping procedures or being linear arrays for use in cutting.Alternatively or additionally, the active electrode(s) may be formed onlateral surfaces of the electrosurgical probe shaft (e.g., in the mannerof a spatula), facilitating access to certain body structures inendoscopic procedures.

[0174] The electrically conductive fluid should have a thresholdconductivity to provide a suitable conductive path between the activeelectrode(s) and the return electrode(s). The electrical conductivity ofthe fluid (in units of millisiemens per centimeter or mS/cm) willusually be greater than 0.2 mS/cm, preferably will be greater than 2mS/cm and more preferably greater than 10 mS/cm. In an exemplaryembodiment, the electrically conductive fluid is isotonic saline, whichhas a conductivity of about 17 mS/cm.

[0175] In some embodiments, the electrode support and the fluid outletmay be recessed from an outer surface of the probe or handpiece toconfine the electrically conductive fluid to the region immediatelysurrounding the electrode support. In addition, the shaft may be shapedso as to form a cavity around the electrode support and the fluidoutlet. This helps to assure that the electrically conductive fluid willremain in contact with the active electrode(s) and the returnelectrode(s) to maintain the conductive path therebetween. In addition,this will help to maintain a vapor or plasma layer between the activeelectrode(s) and the tissue at the treatment site throughout theprocedure, which reduces the thermal damage that might otherwise occurif the vapor layer were extinguished due to a lack of conductive fluid.Provision of the electrically conductive fluid around the target sitealso helps to maintain the tissue temperature at desired levels.

[0176] The voltage applied between the return electrode(s) and theelectrode array will be at high or radio frequency, typically betweenabout 5 kHz and 20 MHz, usually being between about 30 kHz and 2.5 MHz,preferably being between about 50 kHz and 500 kHz, more preferably lessthan 350 kHz, and most preferably between about 100 kHz and 200 kHz. TheRMS (root mean square) voltage applied will usually be in the range fromabout 5 volts to 1000 volts, preferably being in the range from about 10volts to 500 volts depending on the active electrode size, the operatingfrequency and the operation mode of the particular procedure or desiredeffect on the tissue (i.e., contraction, coagulation or ablation).Typically, the peak-to-peak voltage will be in the range of 10 to 2000volts, preferably in the range of 20 to 1200 volts and more preferablyin the range of about 40 to 800 volts (again, depending on the electrodesize, the operating frequency and the operation mode).

[0177] As discussed above, the voltage is usually delivered in a seriesof voltage pulses or alternating current of time varying voltageamplitude with a sufficiently high frequency (e.g., on the order of 5kHz to 20 MHz) such that the voltage is effectively applied continuously(as compared with e.g., lasers claiming small depths of necrosis, whichare generally pulsed at about 10 to 20 Hz). In addition, the duty cycle(i.e., cumulative time in any one-second interval that energy isapplied) is on the order of about 50% for the present invention, ascompared with pulsed lasers which typically have a duty cycle of about0.0001%.

[0178] The preferred power source of the present invention delivers ahigh frequency current selectable to generate average power levelsranging from several milliwatts to tens of watts per electrode,depending on the volume of target tissue being heated, and/or themaximum allowed temperature selected for the probe tip. The power sourceallows the user to select the voltage level according to the specificrequirements of a particular FESS procedure, arthroscopic surgery,dermatological procedure, ophthalmic procedures, open surgery or otherendoscopic surgery procedure. A description of a suitable power sourcecan be found in U.S. Patent Application No. 60/062,997 filed Oct. 23,1997 (Attorney Docket No. 16238-007400), the complete disclosure ofwhich has been incorporated herein by reference.

[0179] The power source may be current limited or otherwise controlledso that undesired heating of the target tissue or surrounding(non-target) tissue does not occur. In one embodiment of the presentinvention, current limiting inductors are placed in series with eachindependent active electrode, where the inductance of the inductor is inthe range of 10 uH to 50,000 uH, depending on the electrical propertiesof the target tissue, the desired tissue heating rate and the operatingfrequency. Alternatively, capacitor-inductor (LC) circuit structures maybe employed, as described previously in co-pending PCT application No.PCT/US94/05168, the complete disclosure of which is incorporated hereinby reference. Additionally, current limiting resistors may be selected.Preferably, these resistors will have a large positive temperaturecoefficient of resistance so that, as the current level begins to risefor any individual active electrode in contact with a low resistancemedium (e.g., saline irrigant or conductive gel), the resistance of thecurrent limiting resistor increases significantly, thereby minimizingthe power delivery from the active electrode into the low resistancemedium (e.g., saline irrigant or conductive gel).

[0180] It should be clearly understood that the invention is not limitedto electrically isolated active electrodes, or even to a plurality ofactive electrodes. For example, the array of active electrodes may beconnected to a single lead that extends through the probe shaft to apower source of high frequency current. Alternatively, the probe mayincorporate a single electrode that extends directly through the probeshaft or is connected to a single lead that extends to the power source.The active electrode may have a ball shape (e.g., for tissuevaporization and desiccation), a twizzle shape (for vaporization andneedle-like cutting), a spring shape (for rapid tissue debulking anddesiccation), a twisted metal shape, an annular or solid tube shape orthe like. Alternatively, the electrode may comprise a plurality offilaments, a rigid or flexible brush electrode (for debulking a tumor,such as a fibroid, bladder tumor or a prostate adenoma), a side-effectbrush electrode on a lateral surface of the shaft, a coiled electrode orthe like. In one embodiment, the probe comprises a single activeelectrode that extends from an insulating member, e.g., ceramic, at thedistal end of the probe. The insulating member is preferably a tubularstructure that separates the active electrode from a tubular or annularreturn electrode positioned proximal to the insulating member and theactive electrode.

[0181] Referring now to FIG. 1, an exemplary electrosurgical system 5for resection, ablation, coagulation and/or contraction of tissue willnow be described in detail. As shown, electrosurgical system 5 generallyincludes an electrosurgical probe 20 connected to a power supply 10 forproviding high frequency voltage to one or more active electrodes and aloop electrode (not shown in FIG. 1) on probe 20. Probe 20 includes aconnector housing 44 at its proximal end, which can be removablyconnected to a probe receptacle 32 of a probe cable 22. The proximalportion of cable 22 has a connector 34 to couple probe 20 to powersupply 10. Power supply 10 has an operator controllable voltage leveladjustment 38 to change the applied voltage level, which is observableat a voltage level display 40. Power supply 10 also includes one or morefoot pedals 24 and a cable 26 which is removably coupled to a receptacle30 with a cable connector 28. The foot pedal 24 may also include asecond pedal (not shown) for remotely adjusting the energy level appliedto active electrodes 104 (FIG. 2), and a third pedal (also not shown)for switching between an ablation mode and a coagulation mode.

[0182] FIGS. 2-5 illustrate an exemplary electrosurgical probe 20constructed according to the principles of the present invention. Asshown in FIG. 2, probe 20 generally includes an elongated shaft 100which may be flexible or rigid, a handle 204 coupled to the proximal endof shaft 100 and an electrode support member 102 coupled to the distalend of shaft 100. Shaft 100 preferably comprises an electricallyconducting material, usually metal, which is selected from the groupconsisting of tungsten, stainless steel alloys, platinum or its alloys,titanium or its alloys, molybdenum or its alloys, and nickel or itsalloys. Shaft 100 includes an electrically insulating jacket 108, whichis typically formed as one or more electrically insulating sheaths orcoatings, such as polytetrafluoroethylene, polyimide, and the like. Theprovision of the electrically insulating jacket over the shaft preventsdirect electrical contact between these metal elements and any adjacentbody structure or the surgeon. Such direct electrical contact between abody structure (e.g., tendon) and an exposed electrode could result inunwanted heating of the structure at the point of contact causingnecrosis.

[0183] Handle 204 typically comprises a plastic material that is easilymolded into a suitable shape for handling by the surgeon. As shown inFIG. 3, handle 204 defines an inner cavity 208 that houses electricalconnections 250 (discussed below), and provides a suitable interface forconnection to an electrical connecting cable 22 (see FIG. 1). As shownin FIG. 5B, the probe will also include a coding resistor 400 having avalue selected to program different output ranges and modes of operationfor the power supply. This allows a single power supply to be used witha variety of different probes in different applications (e.g.,dermatology, cardiac surgery, neurosurgery, arthroscopy, etc). Electrodesupport member 102 extends from the distal end of shaft 100 (usuallyabout 1 to 20 mm), and provides support for a loop electrode 103 and aplurality of electrically isolated active electrodes 104 (see FIG. 4).

[0184] As shown in FIG. 3, the distal portion of shaft 100 is preferablybent to improve access to the operative site of the tissue being treated(e.g., contracted). Electrode support member 102 has a substantiallyplanar tissue treatment surface 212 (see FIG. 4) that is usually at anangle of about 10 to 90 degrees relative to the longitudinal axis ofshaft 100, preferably about 10 to 30 degrees and more preferably about15-18 degrees. In addition, the distal end of the shaft may have abevel, as described in commonly-assigned patent application Ser. No.08/562,332 filed Nov. 22, 1995, now U.S. Pat. No. 6,024,733. Inalternative embodiments, the distal portion of shaft 100 comprises aflexible material which can be deflected relative to the longitudinalaxis of the shaft. Such deflection may be selectively induced bymechanical tension of a pull wire, for example, or by a shape memorywire that expands or contracts by externally applied temperaturechanges. A more complete description of this embodiment can be found inPCT International Application, U.S. National Phase Serial No.PCT/US94/05168.

[0185] The bend in the distal portion of shaft 100 is particularlyadvantageous in arthroscopic treatment of joint tissue as it allows thesurgeon to reach the target tissue within the joint as the shaft 100extends through a cannula or portal. Of course, it will be recognizedthat the shaft may have different angles depending on the procedure. Forexample, a shaft having a 90° bend angle may be particularly useful foraccessing tissue located in the back portion of a joint compartment anda shaft having a 10° to 30° bend angle may be useful for accessingtissue near or in the front portion of the joint compartment.

[0186] As shown in FIG. 4, loop electrode 103 has first and second endsextending from the electrode support member 102. The first and secondends are coupled to, or integral with, a pair of connectors 300, 302,e.g., wires, that extend through the shaft of the probe to its proximalend for coupling to the high frequency power supply. The loop electrodeusually extends about 0.5 to about 10 mm from the distal end of supportmember 102, preferably about 1 to 2 mm. In the representativeembodiment, the loop electrode has a solid construction with asubstantially uniform cross-sectional area, e.g., circular, square, etc.Of course, it will be recognized that the loop or ablation electrode mayhave a wide variety of cross-sectional shapes, such as annular, square,rectangular, L-shaped, V-shaped, D-shaped, C-shaped, star-shaped andcrossed-shaped, as described in commonly-assigned patent applicationSer. No. 08/687,792. In addition, it should be noted that loop electrode103 may have a geometry other than that shown in FIGS. 2-5, such as asemi-circular loop, a V-shaped loop, a straight wire electrode extendingbetween two support members, and the like. Also, loop electrode may bepositioned on a lateral surface of the shaft, or it may extend at atransverse angle from the distal end of the shaft, depending on theparticular surgical procedure.

[0187] Loop electrode 103 usually extends further away from the supportmember than the active electrodes 104 to facilitate resection andablation of tissue. As discussed below, loop electrode 103 is especiallyconfigured for resecting fragments or pieces of tissue, while the activeelectrodes ablate or cause molecular dissociation or disintegration ofthe removed pieces from the fluid environment. In the presentlypreferred embodiment, the probe will include 3 to 7 active electrodespositioned on either side of the loop electrode. The probe may furtherinclude a suction lumen (not shown) for drawing the pieces of tissuetoward the active electrodes after they have been removed from thetarget site by the loop electrode 103.

[0188] Referring to FIG. 4, the electrically isolated active electrodes104 are preferably spaced apart over tissue treatment surface 212 ofelectrode support member 102. The tissue treatment surface andindividual active electrodes 104 will usually have dimensions within theranges set forth above. In the representative embodiment, the tissuetreatment surface 212 has an oval cross-sectional shape with a length Lin the range of 1 mm to 20 mm and a width W in the range from 0.3 mm to7 mm. The oval cross-sectional shape accommodates the bend in the distalportion of shaft 202. The active electrodes 104 preferably extendslightly outward from surface 212, typically by a distance from 0.2 mmto 2. However, it will be understood that electrodes 104 may be flushwith this surface, or even recessed, if desired. In one embodiment ofthe invention, the active electrodes are axially adjustable relative tothe tissue treatment surface so that the surgeon can adjust the distancebetween the surface and the active electrodes.

[0189] In the embodiment shown in FIGS. 2-5, probe 20 includes a returnelectrode 112 for completing the current path between active electrodes104, loop electrode 103 and a high frequency power supply 10 (see FIG.1). As shown, return electrode 112 preferably comprises an annularexposed region of shaft 102 slightly proximal to tissue treatmentsurface 212 of electrode support member 102. Return electrode 112typically has a length of about 0.5 to 10 mm and more preferably about 1to 10 mm. Return electrode 112 is coupled to a connector 250 thatextends to the proximal end of probe 10, where it is suitably connectedto power supply 10 (FIG. 1).

[0190] As shown in FIG. 2, return electrode 112 is not directlyconnected to active electrodes 104 and loop electrode 103. To complete acurrent path from active electrodes 104 or loop electrodes 103 to returnelectrode 112, electrically conductive fluid (e.g., isotonic saline) iscaused to flow therebetween. In the representative embodiment, theelectrically conductive fluid is delivered from a fluid delivery element(not shown) that is separate from probe 20. In arthroscopic surgery, forexample, the joint cavity will be flooded with isotonic saline and theprobe 20 will be introduced into this flooded cavity. Electricallyconductive fluid will be continually re-supplied to maintain theconduction path between return electrode 112 and active electrodes 104and loop electrode 103.

[0191] In alternative embodiments, the fluid path may be formed in probe20 by, for example, an inner lumen or an annular gap (not shown) betweenthe return electrode and a tubular support member within shaft 100. Thisannular gap may be formed near the perimeter of the shaft 100 such thatthe electrically conductive fluid tends to flow radially inward towardsthe target site, or it may be formed towards the center of shaft 100 sothat the fluid flows radially outward. In both of these embodiments, afluid source (e.g., a bag of fluid elevated above the surgical site orhaving a pumping device), is coupled to probe 20 via a fluid supply tube(not shown) that may or may not have a controllable valve. A morecomplete description of an electrosurgical probe incorporating one ormore fluid lumen(s) can be found in commonly assigned, patentapplication Ser. No. 08/485,219, filed on Jun. 7, 1995, now U.S. Pat.No. 5,697,281, the complete disclosure of which is incorporated hereinby reference.

[0192] In addition, probe 20 may include an aspiration lumen (not shown)for aspirating excess conductive fluid, other fluids, such as blood,and/or tissue fragments from the target site. The probe may also includeone or more aspiration electrode(s), such as those described below inreference to FIGS. 8-12, for ablating the aspirated tissue fragments.Alternatively, the aspiration electrode(s) may comprise the activeelectrodes described above. For example, the probe may have anaspiration lumen with a distal opening positioned adjacent one or moreof the active electrodes at the distal end of the probe. As tissuefragments are drawn into the aspiration lumen, the active electrodes areenergized to ablate at least a portion of these fragments to preventclogging of the lumen.

[0193] Referring now to FIG. 6, a surgical kit 300 for resecting and/orablating tissue within a joint according to the invention will now bedescribed. As shown, surgical kit 300 includes a package 302 for housinga surgical instrument 304, and an instructions for use 306 of instrument304. Package 302 may comprise any suitable package, such as a box,carton, wrapping, etc. In the exemplary embodiment, kit 300 furtherincludes a sterile wrapping 320 for packaging and storing instrument304. Instrument 304 includes a shaft 310 having at least one loopelectrode 311 and at least one active electrode 312 at its distal end,and at least one connector (not shown) extending from loop electrode 311and active electrode 312 to the proximal end of shaft 310. Theinstrument 304 is generally disposable after a single procedure.Instrument 304 may or may not include a return electrode 316.

[0194] The instructions for use 306 generally includes the steps ofadjusting a voltage level of a high frequency power supply (not shown)to effect resection and/or ablation of tissue at the target site,connecting the surgical instrument 304 to the high frequency powersupply, positioning the loop electrode 311 and the active electrode 312within electrically conductive fluid at or near the tissue at the targetsite, and activating the power supply. The voltage level is usuallyabout 40 to 400 volts RMS for operating frequencies of about 100 to 200kHz. In a preferred embodiment, the positioning step includesintroducing at least a distal portion of the instrument 304 through aportal into a joint.

[0195] The present invention is particularly useful for lateral releaseprocedures, or for resecting and ablating a bucket-handle tear of themedial meniscus. In the latter technique, the probe is introducedthrough a medial port and the volume which surrounds the working end ofthe probe is filled with an electrically conductive fluid which may, byway of example, be isotonic saline or other biocompatible, electricallyconductive irrigant solution. When a voltage is applied between the loopelectrode and the return electrode, electrical current flows from theloop electrode, through the irrigant solution to the return electrode.The anterior horn is excised by pressing the exposed portion of the loopelectrode into the tear and removing one or more tissue fragments. Thedisplaced fragments are then ablated with the active electrodes asdescribed above.

[0196] Through a central patellar splitting approach, the probe is thenplaced within the joint through the intercondylar notch, and theattached posterior horn insertion is resected by pressing the loopelectrode into the attached posterior fragment. The fragment is thenremoved with the active electrodes and the remnant is checked forstability.

[0197] Referring now to FIG. 7, an exemplary electrosurgical system 411for treatment of tissue in ‘dry fields’ will now be described in detail.Of course, system 411 may also be used in a ‘wet field’, i.e., thetarget site is immersed in electrically conductive fluid. However, thissystem is particularly useful in ‘dry fields’ where the fluid ispreferably delivered through an electrosurgical probe to the targetsite. As shown, electrosurgical system 411 generally comprises anelectrosurgical handpiece or probe 410 connected to a power supply 428for providing high frequency voltage to a target site and a fluid source421 for supplying electrically conductive fluid 450 to probe 410. Inaddition, electrosurgical system 411 may include an endoscope (notshown) with a fiber optic head light for viewing the surgical site,particularly in sinus procedures or procedures in the ear or the back ofthe mouth. The endoscope may be integral with probe 410, or it may bepart of a separate instrument. The system 411 may also include a vacuumsource (not shown) for coupling to a suction lumen or tube in the probe410 for aspirating the target site.

[0198] As shown, probe 410 generally includes a proximal handle 419 andan elongate shaft 418 having an array 412 of active electrodes 458 atits distal end. A connecting cable 434 has a connector 426 forelectrically coupling the active electrodes 458 to power supply 428. Theactive electrodes 458 are electrically isolated from each other and eachof the terminals 458 is connected to an active or passive controlnetwork within power supply 428 by means of a plurality of individuallyinsulated conductors (not shown). A fluid supply tube 415 is connectedto a fluid tube 414 of probe 410 for supplying electrically conductivefluid 450 to the target site.

[0199] Similar to the above embodiment, power supply 428 has an operatorcontrollable voltage level adjustment 430 to change the applied voltagelevel, which is observable at a voltage level display 432. Power supply428 also includes first, second and third foot pedals 437, 438, 439 anda cable 436 which is removably coupled to power supply 428. The footpedals 437, 438, 439 allow the surgeon to remotely adjust the energylevel applied to active electrodes 458. In an exemplary embodiment,first foot pedal 437 is used to place the power supply into the ablationmode and second foot pedal 438 places power supply 428 into the“coagulation” mode. The third foot pedal 439 allows the user to adjustthe voltage level within the “ablation” mode. In the ablation mode, asufficient voltage is applied to the active electrodes to establish therequisite conditions for molecular dissociation of the tissue (i.e.,vaporizing a portion of the electrically conductive fluid, ionizingcharged particles within the vapor layer, and accelerating these chargedparticles against the tissue). As discussed above, the requisite voltagelevel for ablation will vary depending on the number, size, shape andspacing of the electrodes, the distance to which the electrodes extendfrom the support member, etc. Once the surgeon places the power supplyin the ablation mode, voltage level adjustment 430 or third foot pedal439 may be used to adjust the voltage level to adjust the degree oraggressiveness of the ablation.

[0200] Of course, it will be recognized that the voltage and modality ofthe power supply may be controlled by other input devices. However,applicant has found that foot pedals are convenient methods ofcontrolling the power supply while manipulating the probe during asurgical procedure.

[0201] In the coagulation mode, the power supply 428 applies a lowenough voltage to the active electrodes (or the coagulation electrode)to avoid vaporization of the electrically conductive fluid andsubsequent molecular dissociation of the tissue. The surgeon mayautomatically toggle the power supply between the ablation andcoagulation modes by alternately stepping on foot pedals 437, 438,respectively. This allows the surgeon to quickly move betweencoagulation and ablation in situ, without having to remove his/herconcentration from the surgical field or without having to request anassistant to switch the power supply. By way of example, as the surgeonis sculpting soft tissue in the ablation mode, the probe typically willsimultaneously seal and/or coagulate small severed vessels within thetissue. However, larger vessels, or vessels with high fluid pressures(e.g., arterial vessels) may not be sealed in the ablation mode.Accordingly, the surgeon can simply actuate foot pedal 438,automatically lowering the voltage level below the threshold level forablation, and apply sufficient pressure onto the severed vessel for asufficient period of time to seal and/or coagulate the vessel. Afterthis is completed, the surgeon may quickly move back into the ablationmode by actuating foot pedal 437. A specific design of a suitable powersupply for use with the present invention can be found in ProvisionalPatent Application No. 60/062,997 filed Oct. 23, 1997 (Attorney DocketNo. 16238-007400), previously incorporated herein by reference.

[0202] FIGS. 8-10 illustrate an exemplary electrosurgical probe 490constructed according to the principles of the present invention. Asshown in FIG. 8, probe 490 generally includes an elongated shaft 500which may be flexible or rigid, a handle 604 coupled to the proximal endof shaft 500 and an electrode support member 502 coupled to the distalend of shaft 500. Shaft 500 preferably includes a bend 501 that allowsthe distal section of shaft 500 to be offset from the proximal sectionand handle 604. This offset facilitates procedures that require anendoscope, such as FESS, because the endoscope can, for example, beintroduced through the same nasal passage as the shaft 500 withoutinterference between handle 604 and the eyepiece of the endoscope (seeFIG. 16). In one embodiment, shaft 500 preferably comprises a plasticmaterial that is easily molded into the desired shape.

[0203] In an alternative embodiment (not shown), shaft 500 comprises anelectrically conducting material, usually metal, which is selected fromthe group comprising tungsten, stainless steel alloys, platinum or itsalloys, titanium or its alloys, molybdenum or its alloys, and nickel orits alloys. In this embodiment, shaft 500 includes an electricallyinsulating jacket 508 which is typically formed as one or moreelectrically insulating sheaths or coatings, such aspolytetrafluoroethylene, polyimide, and the like. The provision of theelectrically insulating jacket over the shaft prevents direct electricalcontact between these metal elements and any adjacent body structure orthe surgeon. Such direct electrical contact between a body structure(e.g., tendon) and an exposed electrode could result in unwanted heatingand necrosis of the structure at the point of contact.

[0204] Handle 604 typically comprises a plastic material that is easilymolded into a suitable shape for handling by the surgeon. Handle 604defines an inner cavity (not shown) that houses the electricalconnections 650 (FIG. 10), and provides a suitable interface forconnection to an electrical connecting cable 422 (see FIG. 7). Electrodesupport member 502 extends from the distal end of shaft 500 (usuallyabout 1 to 20 mm), and provides support for a plurality of electricallyisolated active electrodes 504 (see FIG. 9). As shown in FIG. 8, a fluidtube 633 extends through an opening in handle 604, and includes aconnector 635 for connection to a fluid supply source, for supplyingelectrically conductive fluid to the target site. Depending on theconfiguration of the distal surface of shaft 500, fluid tube 633 mayextend through a single lumen (not shown) in shaft 500, or it may becoupled to a plurality of lumens (also not shown) that extend throughshaft 500 to a plurality of openings at its distal end. In therepresentative embodiment, fluid tube 633 extends along the exterior ofshaft 500 to a point just proximal of return electrode 512 (see FIG. 9).In this embodiment, the fluid is directed through an opening 637 pastreturn electrode 512 to the active electrodes 504. Probe 490 may alsoinclude a valve 417 (FIG. 8) or equivalent structure for controlling theflow rate of the electrically conductive fluid to the target site.

[0205] As shown in FIG. 8, the distal portion of shaft 500 is preferablybent to improve access to the operative site of the tissue beingtreated. Electrode support member 502 has a substantially planar tissuetreatment surface 612 that is usually at an angle of about 10 to 90degrees relative to the longitudinal axis of shaft 600, preferably about30 to 60 degrees and more preferably about 45 degrees. In alternativeembodiments, the distal portion of shaft 500 comprises a flexiblematerial which can be deflected relative to the longitudinal axis of theshaft. Such deflection may be selectively induced by mechanical tensionof a pull wire, for example, or by a shape memory wire that expands orcontracts by externally applied temperature changes. A more completedescription of this embodiment can be found in PCT InternationalApplication, U.S. National Phase Serial No. PCT/US94/05168, filed on May10, 1994 (Attorney Docket 16238-000440), now U.S. Pat. No. 5,697,909,the complete disclosure of which is incorporated herein by reference.

[0206] The bend in the distal portion of shaft 500 is particularlyadvantageous in the treatment of sinus tissue as it allows the surgeonto reach the target tissue within the nose as the shaft 500 extendsthrough the nasal passage. Of course, it will be recognized that theshaft may have different angles depending on the procedure. For example,a shaft having a 90° bend angle may be particularly useful for accessingtissue located in the back portion of the mouth and a shaft having a 10°to 30° bend angle may be useful for accessing tissue near or in thefront portion of the mouth or nose

[0207] In the embodiment shown in FIGS. 8-10, probe 490 includes areturn electrode 512 for completing the current path between activeelectrodes 504 and a high frequency power supply (e.g., power supply428, FIG. 8). As shown, return electrode 512 preferably comprises anannular conductive band coupled to the distal end of shaft 500 slightlyproximal to tissue treatment surface 612 of electrode support member502, typically about 0.5 to 10 mm and more preferably about 1 to 10 mmfrom support member 502. Return electrode 512 is coupled to a connector658 that extends to the proximal end of probe 409, where it is suitablyconnected to power supply 428 (FIG. 7).

[0208] As shown in FIG. 8, return electrode 512 is not directlyconnected to active electrodes 504. To complete this current path sothat active electrodes 504 are electrically connected to returnelectrode 512, electrically conductive fluid (e.g., isotonic saline) iscaused to flow therebetween. In the representative embodiment, theelectrically conductive fluid is delivered through fluid tube 633 toopening 637, as described above. Alternatively, the fluid may bedelivered by a fluid delivery element (not shown) that is separate fromprobe 490. In arthroscopic surgery, for example, the joint cavity willbe flooded with isotonic saline and the probe 490 will be introducedinto this flooded cavity. Electrically conductive fluid will becontinually re-supplied to maintain the conduction path between returnelectrode 512 and active electrodes 504.

[0209] In alternative embodiments, the fluid path may be formed in probe490 by, for example, an inner lumen or an annular gap between the returnelectrode and a tubular support member within shaft 500. This annulargap may be formed near the perimeter of the shaft 500 such that theelectrically conductive fluid tends to flow radially inward towards thetarget site, or it may be formed towards the center of shaft 500 so thatthe fluid flows radially outward. In both of these embodiments, a fluidsource (e.g., a bag of fluid elevated above the surgical site or havinga pumping device), is coupled to probe 490 via a fluid supply tube (notshown) that may or may not have a controllable valve. A more completedescription of an electrosurgical probe incorporating one or more fluidlumen(s) can be found in parent patent application Ser. No. 08/485,219,filed on Jun. 7, 1995, now U.S. Pat. No. 5,697,281, the completedisclosure of is incorporated herein by reference.

[0210] Referring to FIG. 9, the electrically isolated active electrodes504 are spaced apart over tissue treatment surface 612 of electrodesupport member 502. The tissue treatment surface and individual activeelectrodes 504 will usually have dimensions within the ranges set forthabove. As shown, the probe includes a single, larger opening 609 in thecenter of tissue treatment surface 612, and a plurality of activeelectrodes (e.g., about 3-15) around the perimeter of surface 612 (seeFIG. 9). Alternatively, the probe may include a single, annular, orpartially annular, active electrode at the perimeter of the tissuetreatment surface. The central opening 609 is coupled to a suction lumen(not shown) within shaft 500 and a suction tube 611 (FIG. 8) foraspirating tissue, fluids and/or gases from the target site. In thisembodiment, the electrically conductive fluid generally flows radiallyinward past active electrodes 504 and then back through the opening 609.Aspirating the electrically conductive fluid during surgery allows thesurgeon to see the target site, and it prevents the fluid from flowinginto the patient's body, e.g., through the sinus passages, down thepatient's throat or into the ear canal.

[0211] As shown, one or more of the active electrodes 504 comprise loopelectrodes 540 that extend across distal opening 609 of the suctionlumen within shaft 500. In the representative embodiment, two of theactive electrodes 504 comprise loop electrodes 540 that cross over thedistal opening 609. Of course, it will be recognized that a variety ofdifferent configurations are possible, such as a single loop electrode,or multiple loop electrodes having different configurations than shown.In addition, the electrodes may have shapes other than loops, such asthe coiled configurations shown in FIGS. 11 and 12. Alternatively, theelectrodes may be formed within the suction lumen proximal to the distalopening 609, as shown in FIG. 13. The main function of loop electrodes540 is to ablate portions of tissue that are drawn into the suctionlumen to prevent clogging of the lumen.

[0212] Loop electrodes 540 are electrically isolated from the otheractive electrodes 504, which can be referred to hereinafter as theablation electrodes 504. Loop electrodes 540 may or may not beelectrically isolated from each other. Loop electrodes 540 will usuallyextend only about 0.05 to 4 mm, preferably about 0.1 to 1 mm from thetissue treatment surface of electrode support member 504.

[0213] Of course, it will be recognized that the distal tip of the probemay have a variety of different configurations. For example, the probemay include a plurality of openings 609 around the outer perimeter oftissue treatment surface 612. In this embodiment, the active electrodes504 extend from the center of tissue treatment surface 612 radiallyinward from openings 609. The openings are suitably coupled to fluidtube 633 for delivering electrically conductive fluid to the targetsite, and a suction tube 611 for aspirating the fluid after it hascompleted the conductive path between the return electrode 512 and theactive electrodes 504. In this embodiment, the ablation activeelectrodes 504 are close enough to openings 609 to ablate most of thelarge tissue fragments that are drawn into these openings.

[0214]FIG. 10 illustrates the electrical connections 650 within handle604 for coupling active electrodes 504 and return electrode 512 to thepower supply 428. As shown, a plurality of wires 652 extend throughshaft 500 to couple terminals 504 to a plurality of pins 654, which areplugged into a connector block 656 for coupling to a connecting cable422 (FIG. 7). Similarly, return electrode 512 is coupled to connectorblock 656 via a wire 658 and a plug 660.

[0215] In use, the distal portion of probe 490 is introduced to thetarget site (either endoscopically, through an open procedure, ordirectly onto the patient's skin) and active electrodes 504 arepositioned adjacent to tissue at the target site. Electricallyconductive fluid is delivered through tube 633 and opening 637 to thetissue. The fluid flows past the return electrode 512 to the activeelectrodes 504 at the distal end of the shaft. The rate of fluid flow iscontrolled with valve 417 (FIG. 7) such that the zone between the tissueand electrode support 502 is constantly immersed in the fluid. The powersupply 428 is then turned on and adjusted such that a high frequencyvoltage difference is applied between active electrodes 504 and returnelectrode 512. The electrically conductive fluid provides the conductionpath between active electrodes 504 and the return electrode 512.

[0216] In the representative embodiment, the high frequency voltage issufficient to convert the electrically conductive fluid (not shown)between the target tissue and active electrodes 504 into an ionizedvapor layer or plasma (not shown). As a result of the applied voltagedifference between active electrode(s) 504 and the target tissue (i.e.,the voltage gradient across the plasma layer), charged particles in theplasma (e.g., electrons) are accelerated towards the tissue. Atsufficiently high voltage differences, these charged particles gainsufficient energy to cause dissociation of the molecular bonds withintissue structures. This molecular dissociation is accompanied by thevolumetric removal (i.e., ablative sublimation) of tissue and theproduction of low molecular weight gases, such as oxygen, nitrogen,carbon dioxide, hydrogen and methane. The short range of the acceleratedcharged particles within the tissue confines the molecular dissociationprocess to the surface layer to minimize damage and necrosis to theunderlying tissue.

[0217] During the process, the gases will be aspirated through opening609 and suction tube 611 to a vacuum source or collection reservoir (notshown). In addition, excess electrically conductive fluid and otherfluids (e.g., blood) will be aspirated from the target site tofacilitate the surgeon's view. Applicant has also found that tissuefragments are also aspirated through opening 609 into suction lumen andtube 611 during the procedure. These tissue fragments are ablated ordissociated with loop electrodes 540 with a similar mechanism describedabove. Namely, as electrically conductive fluid and tissue fragments areaspirated towards loop electrodes 540, these electrodes are activated sothat a high frequency voltage is applied to loop electrodes 540 andreturn electrode 512 (of course, the probe may include a different,separate return electrode for this purpose). The voltage is sufficientto vaporize the fluid, and create a plasma layer between loop electrodes540 and the tissue fragments so that portions of the tissue fragmentsare ablated or removed. This reduces the volume of the tissue fragmentsas they pass through suction lumen to minimize clogging of the lumen.

[0218] In addition, the present invention is particularly useful forremoving elastic tissue, such as the synovial tissue found in joints. Inarthroscopic procedures, this elastic synovial tissue tends to move awayfrom instruments within the conductive fluid, making it difficult forconventional instruments to remove this tissue. With the presentinvention, the probe is moved adjacent the target synovial tissue, andthe vacuum source is activated to draw the synovial tissue towards thedistal end of the probe. The aspiration and/or active electrodes arethen energized to ablate this tissue. This allows the surgeon to quicklyand precisely ablate elastic tissue with minimal thermal damage to thetreatment site.

[0219] In one embodiment, loop electrodes 540 are electrically isolatedfrom the other active electrodes 504, and electrodes 540 must beseparately activated by power supply 428. In other embodiments, loopelectrodes 540 will be activated at the same time that active electrodes504 are activated. In this case, applicant has found that the plasmalayer typically forms when tissue is drawn adjacent to loop electrodes540.

[0220] Referring now to FIGS. 11 and 12, alternative embodiments foraspiration electrodes will now be described. As shown in FIG. 11, theaspiration electrodes may comprise a pair of coiled electrodes 550 thatextend across distal opening 609 of the suction lumen. The largersurface area of the coiled electrodes 550 usually increases theeffectiveness of the electrodes 550 in ablating tissue fragments passingthrough opening 609. In FIG. 12, the aspiration electrode comprises asingle coiled electrode 552 passing across the distal opening 609 ofsuction lumen. This single electrode 552 may be sufficient to inhibitclogging of the suction lumen. Alternatively, the aspiration electrodesmay be positioned within the suction lumen proximal to the distalopening 609. Preferably, these electrodes are close to opening 609 sothat tissue does not clog the opening 609 before it reaches electrode(s)554. In this embodiment, a separate return electrode 556 may be providedwithin the suction lumen to confine the electric currents therein.

[0221] Referring to FIG. 13, another embodiment of the present inventionincorporates an aspiration electrode 560 within the aspiration lumen 562of the probe. As shown, the electrode 560 is positioned just proximal ofdistal opening 609 so that the tissue fragments are ablated as theyenter lumen 562. In the representative embodiment, the aspirationelectrode 560 comprises a loop electrode that extends across theaspiration lumen 562. However, it will be recognized that many otherconfigurations are possible. In this embodiment, the return electrode564 is located on the exterior of the probe, as in the previouslydescribed embodiments. Alternatively, the return electrode(s) may belocated within the aspiration lumen 562 with the aspiration electrode560. For example, the inner insulating coating 563 may be exposed atportions within the lumen 562 to provide a conductive path between thisexposed portion of return electrode 564 and the aspiration electrode560. The latter embodiment has the advantage of confining the electriccurrents to within the aspiration lumen. In addition, in dry fields inwhich the conductive fluid is delivered to the target site, it isusually easier to maintain a conductive fluid path between the activeand return electrodes in the latter embodiment because the conductivefluid is aspirated through the aspiration lumen 562 along with thetissue fragments.

[0222] FIGS. 14-17 illustrate a method for treating nasal or sinusblockages, e.g., chronic sinusitis, according to the present invention.In these procedures, the polyps, turbinates or other sinus tissue may beablated or reduced (e.g., by tissue contraction) to clear the blockageand/or enlarge the sinus cavity to reestablish normal sinus function.For example, in chronic rhinitis, which is a collective term for chronicirritation or inflammation of the nasal mucosa with hypertrophy of thenasal mucosa, the inferior turbinate may be reduced by ablation orcontraction. Alternatively, a turbinectomy or mucotomy may be performedby removing a strip of tissue from the lower edge of the inferiorturbinate to reduce the volume of the turbinate. For treating nasalpolypi, which comprises benign pedicled or sessile masses of nasal orsinus mucosa caused by inflammation, the nasal polypi may be contractedor shrunk, or ablated by the method of the present invention. Fortreating severe sinusitis, a frontal sinus operation may be performed tointroduce the electrosurgical probe to the site of blockage. The presentinvention may also be used to treat diseases of the septum, e.g.,ablating or resecting portions of the septum for removal, straighteningor reimplantation of the septum.

[0223] The present invention is particularly useful in functionalendoscopic sinus surgery (FESS) in the treatment of sinus disease. Incontrast to prior art microdebriders, the electrosurgical probe of thepresent invention effects hemostasis of severed blood vessels, andallows the surgeon to precisely remove tissue with minimal or no damageto surrounding tissue, bone, cartilage or nerves. By way of example andnot limitation, the present invention may be used for the followingprocedures: (1) uncinectomy or medial displacement or removal ofportions of the middle turbinate; (2) maxillary, sphenoid or ethmoidsinusotomies or enlargement of the natural ostium of the maxillary,sphenoid, or ethmoid sinuses, respectively; (3) frontal recessdissections, in which polypoid or granulation tissue are removed; (4)polypectomies, wherein polypoid tissue is removed in the case of severenasal polyposis; (5) concha bullosa resections or the thinning ofpolypoid middle turbinate; (6) septoplasty; and the like.

[0224] FIGS. 14-17 schematically illustrate an endoscopic sinus surgery(FESS) procedure according to the present invention. As shown in FIG.14, an endoscope 700 is first introduced through one of the nasalpassages 701 to allow the surgeon to view the target site, e.g., thesinus cavities. As shown, the endoscope 700 will usually comprise a thinmetal tube 702 with a lens (not shown) at the distal end 704, and aneyepiece 706 at the proximal end 708. As shown in FIG. 8, the probeshaft 500 has a bend 501 to facilitate use of both the endoscope and theprobe 490 in the same nasal passage (i.e., the handles of the twoinstruments do not interfere with each other in this embodiment).Alternatively, the endoscope may be introduced transorally through theinferior soft palate to view the nasopharynx. Suitable nasal endoscopesfor use with the present invention are described in U.S. Pat. Nos.4,517,962, 4,844,052, 4,881,523 and 5,167,220, the complete disclosuresof which are incorporated herein by reference for all purposes.

[0225] Alternatively, the endoscope 700 may include a sheath (not shown)having an inner lumen for receiving the electrosurgical probe shaft 500.In this embodiment, the shaft 500 will extend through the inner lumen toa distal opening in the endoscope. The shaft will include suitableproximal controls for manipulation of its distal end during the surgicalprocedure.

[0226] As shown in FIG. 15, the distal end of probe 490 is introducedthrough nasal passage 701 into the nasal cavity 703 (endoscope 700 isnot shown in FIG. 15). Depending on the location of the blockage, theactive electrodes 504 will be positioned adjacent the blockage in thenasal cavity 703, or in one of the paranasal sinuses 705, 707. Note thatonly the frontal sinus 705 and the sphenoidal sinus 707 are shown inFIG. 15, but the procedure is also applicable to the ethmoidal andmaxillary sinuses. Once the surgeon has reached the point of majorblockage, electrically conductive fluid is delivered through tube 633and opening 637 to the tissue (see FIG. 8). The fluid flows past thereturn electrode 512 to the active electrodes 504 at the distal end ofthe shaft. The rate of fluid flow is controlled by valve 417 (FIG. 8)such that the zone between the tissue and electrode support 502 isconstantly immersed in the fluid. The power supply 428 is then turned onand adjusted such that a high frequency voltage difference is appliedbetween active electrodes 504 and return electrode 512. The electricallyconductive fluid provides the conduction path between active electrodes504 and the return electrode 512.

[0227]FIGS. 16A and 16B illustrate the removal of sinus tissue in moredetail. As shown, the high frequency voltage is sufficient to convertthe electrically conductive fluid (not shown) between the target tissue702 and active electrode(s) 504 into an ionized vapor layer 712 orplasma. As a result of the applied voltage difference between activeelectrode(s) 504 (or active electrode 458) and the target tissue 702(i.e., the voltage gradient across the plasma layer 712), chargedparticles 715 in the plasma (e.g., electrons) are accelerated. Atsufficiently high voltage differences, these charged particles 715 gainsufficient energy to cause dissociation of the molecular bonds withintissue structures in contact with the plasma field. This moleculardissociation is accompanied by the volumetric removal (i.e., ablativesublimation) of tissue and the production of low molecular weight gases714, such as oxygen, nitrogen, carbon dioxide, hydrogen and methane. Theshort range of the accelerated charged particles 715 within the tissueconfines the molecular dissociation process to the surface layer tominimize damage and necrosis to the underlying tissue 720.

[0228] During the process, the gases 714 will be aspirated throughopening 609 and suction tube 611 to a vacuum source. In addition, excesselectrically conductive fluid, and other fluids (e.g., blood) will beaspirated from the target site 700 to facilitate the surgeon's view.During ablation of the tissue, the residual heat generated by thecurrent flux lines, will usually be sufficient to coagulate any severedblood vessels at the site. Typically, the temperature of the treatedtissue is less than 150° C. If the residual heat is not sufficient tocoagulate severed blood vessels, the surgeon may switch the power supply428 into the coagulation mode by lowering the voltage to a level belowthe threshold for fluid vaporization, as discussed above. Thissimultaneous hemostasis results in less bleeding and facilitates thesurgeon's ability to perform the procedure. Once the blockage has beenremoved, aeration and drainage are reestablished to allow the sinuses toheal and return to their normal function.

[0229] FIGS. 18-22 illustrate another embodiment of the presentinvention. As shown in FIG. 18, an electrosurgical probe 800 includes anelongated shaft 801 which may be flexible or rigid, a handle 804 coupledto the proximal end of shaft 801 and an electrode support member 802coupled to the distal end of shaft 801. As in previous embodiments,probe 800 includes an active loop electrode 803 (e.g., FIG. 20) and areturn electrode 812 (not shown), the latter spaced proximally fromactive loop electrode 803. The probe 800 further includes a suctionlumen 820 (FIG. 19) for aspirating excess fluids, bubbles, tissuefragments, and/or products of ablation from the target site. As shown inFIGS. 19 and 22, suction lumen 820 extends through support member 802 toa distal opening 822, and extends through shaft 801 and handle 804 to anexternal connector 824 for coupling to a vacuum source. Typically, thevacuum source is a standard hospital pump that provides suction pressureto connector 824 and lumen 820.

[0230] As shown in FIG. 19, handle 804 defines an inner cavity 808 thathouses the electrical connections 850 (discussed above), and provides asuitable interface for connection to an electrical connecting cable 22(see FIG. 1). As shown in FIG. 21, the probe will also include a codingresistor 860 having a value selected to program different output rangesand modes of operation for the power supply. This allows a single powersupply to be used with a variety of different probes in differentapplications (e.g., dermatology, cardiac surgery, neurosurgery,arthroscopy, etc).

[0231] Electrode support member 802 extends from the distal end of shaft801 (usually about 1 to 20 mm), and provides support for loop electrode803 and a ring electrode 804 (see FIG. 22). As shown in FIG. 20, loopelectrode 803 has first and second ends extending from the electrodesupport member 802. The first and second ends are each coupled to, orintegral with, one or more connectors, e.g., wires (not shown), thatextend through the shaft of the probe to its proximal end for couplingto the high frequency power supply. The loop electrode usually extendsabout 0.5 to about 10 mm from the distal end of support member,preferably about 1 to 2 mm. Loop electrode 803 usually extends furtheraway from the support member than the ring electrode 804 to facilitateablation of tissue. As discussed below, loop electrode 803 is especiallyconfigured for tissue ablation, while the ring electrode 804 ablatestissue fragments that are aspirated into suction lumen 820.

[0232] Referring to FIG. 22, ring electrode 804 preferably comprises atungsten or titanium wire having two ends 830, 832 coupled to electricalconnectors (not shown) within support member 802. The wire is bent toform one-half of a figure eight, thereby forming a ring positioned overopening 822 of suction lumen 820. This ring inhibits passage of tissuefragments large enough to clog suction lumen 820. Moreover, voltagesapplied between ring electrode 804 and return electrode 812 providesufficient energy to ablate these tissue fragments into smallerfragments that are then aspirated through lumen 820. In a presentlypreferred embodiment, ring electrode 804 and loop electrode 803 areelectrically isolated from each other. However, electrodes 804, 803 maybe electrically coupled to each other in some applications.

[0233] FIGS. 25-31 illustrate another embodiment of the presentinvention including an electrosurgical probe 900 incorporating an activescreen electrode 902. As shown in FIG. 25, probe 900 includes anelongated shaft 904 which may be flexible or rigid, a handle 906 coupledto the proximal end of shaft 904 and an electrode support member 908coupled to the distal end of shaft 904. Probe 900 further includes anactive screen electrode 902 and a return electrode 910 spaced proximallyfrom active screen electrode 902. In this embodiment, active screenelectrode 902 and support member 908 are configured such that the activeelectrode 902 is positioned on a lateral side of the shaft 904 (e.g., 90degrees from the shaft axis) to allow the physician to access tissuethat is offset from the axis of the portal or arthroscopic opening intothe joint cavity in which the shaft 904 passes during the procedure. Toaccomplish this, probe 900 includes an electrically insulating cap 920coupled to the distal end of shaft 904 and having a lateral opening 922for receiving support member 908 and screen electrode 902.

[0234] The probe 900 further includes a suction connection tube 914 forcoupling to a source of vacuum, and an inner suction lumen 912 (FIG. 26)for aspirating excess fluids, tissue fragments, and/or products ofablation (e.g., bubbles) from the target site. In addition, suctionlumen 912 allows the surgeon to draw loose tissue, e.g., synovialtissue, towards the screen electrode 902, as discussed above. Typically,the vacuum source is a standard hospital pump that provides suctionpressure to connection tube 914 and lumen 912. However, a pump may alsobe incorporated into the high frequency power supply. As shown in FIGS.26, 27 and 30, internal suction lumen 912, which preferably comprisespeek tubing, extends from connection tube 914 in handle 906, throughshaft 904 to an axial opening 916 in support member 908, through supportmember 908 to a lateral opening 918. Lateral opening 918 contacts screenelectrode 902, which includes a plurality of holes 924 (FIG. 28) forallowing aspiration therethrough, as discussed below.

[0235] As shown in FIG. 26, handle 906 defines an inner cavity 926 thathouses the electrical connections 928 (discussed above), and provides asuitable interface for connection to an electrical connecting cable 22(see FIG. 1). As shown in FIG. 29, the probe will also include a codingresistor 930 having a value selected to program different output rangesand modes of operation for the power supply. This allows a single powersupply to be used with a variety of different probes in differentapplications (e.g., dermatology, cardiac surgery, neurosurgery,arthroscopy, etc).

[0236] Referring to FIG. 29, electrode support member 908 preferablycomprises an inorganic material, such as glass, ceramic, siliconnitride, alumina or the like, that has been formed with lateral andaxial openings 918, 916 for suction, and with one or more smaller holes930 for receiving electrical connectors 932. In the representativeembodiment, support member 908 has a cylindrical shape for supporting acircular screen electrode 902. Of course, screen electrode 902 may havea variety of different shapes, such as the rectangular shape shown inFIG. 31, which may change the associated shape of support member 908. Asshown in FIG. 27, electrical connectors 932 extend from connections 928,through shaft 904 and holes 930 in support member 908 to screenelectrode 902 to couple the active electrode 902 to a high frequencypower supply. In the representative embodiment, screen electrode 902 ismounted to support member 908 by ball wires 934 that extend throughholes 936 in screen electrode 902 and holes 930 in support member 908.Ball wires 934 function to electrically couple the screen 902 toconnectors 932 and to secure the screen 902 onto the support member 908.Of course, a variety of other methods may be used to accomplish thesefunctions, such as nailhead wires, adhesive and standard wires, achannel in the support member, etc.

[0237] The screen electrode 902 will comprise a conductive material,such as tungsten, titanium, molybdenum, stainless steel, aluminum, gold,copper or the like. In some embodiments, it may be advantageous toconstruct the active and return electrodes of the same material toeliminate the possibility of DC currents being created by dissimilarmetal electrodes. Screen electrode 902 will usually have a diameter inthe range of about 0.5 to 8 mm, preferably about 1 to 4 mm, and athickness of about 0.05 to about 2.5 mm, preferably about 0.1 to 1 mm.Electrode 902 will comprise a plurality of holes 924 having sizes thatmay vary depending on the particular application and the number of holes(usually from one to 50 holes, and preferably about 3 to 20 holes).Holes 924 will typically be large enough to allow ablated tissuefragments to pass through into suction lumen 912, typically being about2 to 30 mils in diameter, preferably about 5 to 20 mils in diameter. Insome applications, it may be desirable to only aspirate fluid and thegaseous products of ablation (e.g., bubbles) so that the holes may bemuch smaller, e.g., on the order of less than 10 mils, often less than 5mils.

[0238] In the representative embodiment, probe 900 is manufactured asfollows: screen electrode 902 is placed on support member 908 so thatholes 924 are lined up with holes 930. One or more ball wires 934 areinserted through these holes, and a small amount of adhesive (e.g.,epotek) is placed around the outer face of support member 908. The ballwires 934 are then pulled until screen 902 is flush with support member908, and the entire sub-assembly is cured in an oven or other suitableheating mechanism. The electrode-support member sub-assembly is theninserted through the lateral opening in cap 920 and adhesive is appliedto the peek tubing suction lumen 912. The suction lumen 912 is thenplaced through axial hole 916 in support member 908 and thissub-assembly is cured. The return electrode 910 (which is typically theexposed portion of shaft 904) is then adhered to cap 920.

[0239] Another advantage of the present invention is the ability toprecisely ablate layers of sinus tissue without causing necrosis orthermal damage to the underlying and surrounding tissues, nerves (e.g.,the optic nerve) or bone. In addition, the voltage can be controlled sothat the energy directed to the target site is insufficient to ablatebone or adipose tissue (which generally has a higher impedance than thetarget sinus tissue). In this manner, the surgeon can literally cleanthe tissue off the bone, without ablating or otherwise effectingsignificant damage to the bone.

[0240] Methods for treating air passage disorders according to thepresent invention will now be described. In these embodiments, anelectrosurgical probe such as one described above can be used to ablatetargeted masses including, but not limited to, the tongue, tonsils,turbinates, soft palate tissues (e.g., the uvula), hard tissue andmucosal tissue. In one embodiment, selected portions of the tongue 714are removed to treat sleep apnea. In this method, the distal end of anelectrosurgical probe 490 is introduced into the patient's mouth 710, asshown in FIG. 17. An endoscope (not shown), or other type of viewingdevice, may also be introduced, or partially introduced, into the mouth710 to allow the surgeon to view the procedure (the viewing device maybe integral with, or separate from, the electrosurgical probe). Theactive electrodes 504 are positioned adjacent to or against the backsurface 716 of the tongue 714, and electrically conductive fluid isdelivered to the target site, as described above. The power supply 428is then activated to remove selected portions of the back of the tongue714, as described above, without damaging sensitive structures, such asnerves, and the bottom portion of the tongue 714.

[0241] In another embodiment, the electrosurgical probe of the presentinvention can be used to ablate and/or contract soft palate tissue totreat snoring disorders. In particular, the probe is used to ablate orshrink sections of the uvula 720 without causing unwanted tissue damageunder and around the selected sections of tissue. For tissuecontraction, a sufficient voltage difference is applied between theactive electrodes 504 and the return electrode 512 to elevate the uvulatissue temperature from normal body temperatures (e.g., 37° C.) totemperatures in the range of 45° C. to 90° C., preferably in the rangefrom 60° C. to 70° C. This temperature elevation causes contraction ofthe collagen connective fibers within the uvula tissue.

[0242] In addition to the above procedures, the system and method of thepresent invention may be used for treating a variety of disorders in themouth 710, pharynx 730, larynx 735, hypopharynx, trachea 740, esophagus750 and the neck 760. For example, tonsillar hyperplasia or other tonsildisorders may be treated with a tonsillectomy by partially ablating thelymphoepithelial tissue. This procedure is usually carried out underintubation anesthesia with the head extended. An incision is made in theanterior faucial pillar, and the connective tissue layer between thetonsillar parenchyma and the pharyngeal constrictor muscles isdemonstrated. The incision may be made with conventional scalpels, orwith the electrosurgical probe of the present invention. The tonsil isthen freed by ablating through the upper pole to the base of the tongue,preserving the faucial pillars. The probe ablates the tissue, whileproviding simultaneous hemostasis of severed blood vessels in theregion. Similarly, adenoid hyperplasia, or nasal obstruction leading tomouth breathing difficulty, can be treated in an adenoidectomy byseparating (e.g., resecting or ablating) the adenoid from the base ofthe nasopharynx.

[0243] Other pharyngeal disorders can be treated according to thepresent invention. For example, hypopharyngeal diverticulum involvessmall pouches that form within the esophagus immediately above theesophageal opening. The sac of the pouch may be removed endoscopicallyaccording to the present invention by introducing a rigid esophagoscope,and isolating the sac of the pouch. The cricopharyngeus muscle is thendivided, and the pouch is ablated according to the present invention.Tumors within the mouth and pharynx, such as hemangiomas, lymphangiomas,papillomas, lingual thyroid tumors, or malignant tumors, may also beremoved according to the present invention.

[0244] Other procedures of the present invention include removal ofvocal cord polyps and lesions and partial or total laryngectomies. Inthe latter procedure, the entire larynx is removed from the base of thetongue to the trachea, if necessary with removal of parts of the tongue,the pharynx, the trachea and the thyroid gland.

[0245] Tracheal stenosis may also be treated according to the presentinvention. Acute and chronic stenoses within the wall of the trachea maycause coughing, cyanosis and choking.

[0246]FIG. 23 schematically illustrates a lipectomy procedure in theabdomen according to the present invention. In a conventionalliposuction procedure according to the prior art, multiple incisions aremade to allow cross-tunneling, and the surgeon will manipulate thesuction cannula in a linear piston-like motion during suction to removethe adipose tissue to avoid clogging of the cannula, and to facilitateseparation of the fatty tissue from the remaining tissue. The presentinvention mostly solves these two problems and, therefore, minimizes theneed for the surgeon to manipulate the probe in such a fashion.

[0247] Liposuction in the abdomen, lower torso and thighs according tothe present invention removes the subcutaneous fat in these regionswhile leaving the fascial, neurovascular and lymphatic network intact oronly mildly compromised. As shown, access incisions 1200 are typicallypositioned in natural skin creases remote from the areas to beliposuctioned. As shown in FIG. 23, the distal portion (not shown) of anelectrosurgical instrument 1202 is introduced through one or more of theincisions 1200 and one or more active electrode(s) 1004 (FIG. 33) arepositioned adjacent the fatty tissue. Electrically conductive fluid,e.g., isotonic saline, is delivered through tube 1133 and opening 1137to the tissue. The fluid flows past the return electrode 1012 to theactive electrodes 1004 at the distal end of the shaft. The rate of fluidflow is controlled by a valve such that the zone between the tissue andelectrode support 1002 is constantly immersed in the fluid. The powersupply 928 is then turned on and adjusted such that a high frequencyvoltage difference is applied between active electrodes 1004 and returnelectrode 1012. The electrically conductive fluid provides theconduction path between active electrodes 1004 and the return electrode1012.

[0248] In the representative embodiment, the high frequency voltage issufficient to convert the electrically conductive fluid (not shown)between the target tissue and active electrodes 1004 into an ionizedvapor layer or plasma (not shown). As a result of the applied voltagedifference between active electrode(s) 1004 and the target tissue (i.e.,the voltage gradient across the plasma layer), charged particles in theplasma (e.g., electrons) are accelerated towards the fatty tissue. Atsufficiently high voltage differences, these charged particles gainsufficient energy to cause dissociation of the molecular bonds withintissue structures. This molecular dissociation is accompanied by thevolumetric removal (i.e., ablative sublimation) of tissue and theproduction of low molecular weight gases, such as oxygen, nitrogen,carbon dioxide, hydrogen and methane. The short range of the acceleratedcharged particles within the tissue confines the molecular dissociationprocess to the surface layer to minimize damage and necrosis to theunderlying tissue.

[0249] In alternative embodiments, the high frequency voltage issufficient to heat and soften or separate portions of the fatty tissuefrom the surrounding tissue. Suction is then applied from a vacuumsource (not shown) through lumen 962 to aspirate or draw away the heatedfatty tissue. A temperature of about 45° C. softens fatty tissue, and atemperature of about 50° C. normally liquefies mammalian adipose tissue.This heating and softening of the fatty tissue reduces the collateraldamage created when the heated tissue is then removed throughaspiration. Alternatively, the present invention may employ acombination of ablation through molecular dissociation, as describedabove, and heating or softening of the fatty tissue. In this embodiment,some of the fatty tissue is ablated in situ, while other portions aresoftened to facilitate removal through suction.

[0250] During the process, the gases will be aspirated through thesuction tube to a vacuum source. In addition, excess electricallyconductive fluid, and other fluids (e.g., blood) will be aspirated fromthe target site to facilitate the surgeon's view. Applicant has alsofound that tissue fragments are also aspirated through opening 1109 intosuction lumen and tube 1111 during the procedure. These tissue fragmentsare ablated or dissociated with loop electrodes 1040 in a similarmechanism to that described above. That is, as electrically conductivefluid and tissue fragments are aspirated towards loop electrodes 1040,these electrodes 1040 are activated so that a high frequency voltage isapplied between loop electrodes 1040 and return electrode 1012 (ofcourse, the probe may include a different, separate return electrode forthis purpose). The voltage is sufficient to vaporize the fluid, andcreate a plasma layer between loop electrodes 1040 and the tissuefragments so that portions of the tissue fragments are ablated orremoved. This reduces the volume of the tissue fragments as they passthrough suction lumen to minimize clogging of the lumen.

[0251] In one embodiment, loop electrodes 1040 are electrically isolatedfrom the other active electrodes 1004, and electrodes 1040 must beseparately activated at the power supply 928. In other embodiments, loopelectrodes 1040 will be activated at the same time that activeelectrodes 1004 are activated. In this case, applicant has found thatthe plasma layer typically forms when tissue is drawn adjacent to loopelectrodes 1040.

[0252]FIG. 24 illustrates a cervical liposuction procedure in the faceand neck according to the present invention. As shown, the distalportion of the electrosurgical probe 1202 may be inserted in eithersubmental or retroauricular incisions 1204 in the face and neck. In thisprocedure, the probe 1202 is preferably passed through a portion of thefatty tissue with the power supply 928 activated, but without suction toestablish a plane of dissection at the most superficial level of desiredfat removal. This plane of dissection allows a smooth, supple,re-draping of the region after liposuction has been completed. If this“pre-tunneling” is not performed in this region, the cannula has atendency to pull the skin inward, creating small pockets andindentations in the skin, which become evident as superficialirregularities after healing. Pre-tunneling also enables accurate, safeand proper removal of fat deposits while preserving a fine cushion ofsub-dermal fat.

[0253] The present invention may also be used to perform lipectomies incombination with face and neck lifts to facilitate the latterprocedures. After the cervical liposuction is complete, the skin flapsare elevated in the temporal, cheek and lateral regions. The lateralneck skin flap dissection is greatly facilitated by the previous suctionlipectomy in that region, and the medial and central skin flap elevationmay be virtually eliminated.

[0254] In another embodiment, the present invention comprises anelectrified shaver or microdebrider. Powered instrumentation, such asmicrodebrider devices and shavers, has been used to remove polyps orother swollen tissue in functional endoscopic sinus surgery and synovialand meniscus tissue and articular cartilage I arthroscopic procedures.These powered instruments are disposable motorized cutters having arotating shaft with a serrated distal tip for cutting and resectingtissue. The handle of the microdebrider is typically hollow, and itaccommodates a small vacuum, which serves to aspirate debris. In thisprocedure, the distal tip of the shaft is endoscopically delivered to atarget site of the patient's body, and an external motor rotates theshaft and the serrated tip, allowing the tip to cut tissue, which isthen aspirated through the instrument.

[0255] While microdebriders and shavers of the prior art have shown somepromise, these devices suffer from a number of disadvantages. For onething, these devices sever blood vessels within the tissue, usuallycausing profuse bleeding that obstructs the surgeon's view of the targetsite. Controlling this bleeding can be difficult since the vacuumingaction tends to promote hemorrhaging from blood vessels disrupted duringthe procedure. In addition, usually the microdebrider or shaver of theprior art must be periodically removed from the patient to cauterizesevered blood vessels, thereby lengthening the procedure. Moreover, theserrated edges and other fine crevices of the microdebrider and shavercan easily become clogged with debris, which requires the surgeon toremove and clean the microdebrider during the surgery, furtherincreasing the length of the procedure.

[0256] The present invention solves the above problems by providing oneor more active electrodes at the distal tip of the aspiration instrumentto effect hemostasis of severed blood vessels at the target site. Thisminimizes bleeding to clear the surgical site, and to reducepostoperative swelling and pain. In addition, by providing an aspirationelectrode on or near the suction lumen, as described above, the presentinvention avoids the problems of clogging inherent with these devices.

[0257] The systems of the present invention may include a bipolararrangement of electrodes designed to ablate tissue at the target site,and then aspirate tissue fragments, as described above. Alternatively,the instrument may also include a rotating shaft with a cutting tip forcutting tissue in a conventional manner. In this embodiment, theelectrode(s) serve to effect hemostasis at the target site and to reduceclogging of the aspiration lumen, while the rotating shaft and cuttingtip do the bulk of tissue removal by cutting the tissue in aconventional manner.

[0258] The system and method of the present invention may also be usefulto efficaciously ablate (i.e., disintegrate) cancer cells and tissuecontaining cancer cells, such as cancer on the surface of the epidermis,eye, colon, bladder, cervix, uterus and the like. The presentinvention's ability to completely disintegrate the target tissue can beadvantageous in this application because simply vaporizing andfragmenting cancerous tissue may lead to spreading of viable cancercells (i.e., seeding) to other portions of the patient's body or to thesurgical team in close proximity to the target tissue. In addition, thecancerous tissue can be removed to a precise depth while minimizingnecrosis of the underlying tissue.

[0259] In another aspect of the invention, systems and methods areprovided for treating articular cartilage defects, such as chondralfractures or chondromalicia. The method comprises positioning a distalend of an electrosurgical instrument, such as a probe or a catheter,into close proximity to an articular cartilage surface, eitherarthroscopically or through an open procedure. High frequency voltage isthen applied between an active electrode on the instrument and a returnelectrode such that electric current flows therebetween and sufficientenergy is imparted to the articular cartilage to smooth its surface orto reduce a level of fibrillation in the cartilage. In treatingchondromalicia, the voltage between the electrodes is sufficient to heat(e.g., shrink) or ablate (i.e., remove) cartilage strands extending fromthe articular cartilage surface. In treating chondral fractures, lesionsor other defects, the voltage is typically sufficient to ablate or heatat least a portion of the diseased tissue while leaving behind a smooth,contoured surface. In both cases, the method preferably includes forminga substantially continuous matrix layer on the surface of the tissue toseal the tissue, insulating the fracturing and fissuring within thearticular cartilage that can cause further degeneration.

[0260] The present invention provides a highly controlled application ofenergy across the articular cartilage, confining the effect to thesurface to produce precise and anatomically optimal tissue sculptingthat stabilizes the articular cartilage and minimizes collateral tissueinjury. Results to date demonstrate that cultures of post-treatedchondrocytes within the cartilage tissue remain viable for at least onemonth, confirming that remaining chrondrocytes remain viable after thisprocedure. Moreover, minimal to no collagen abnormalities have beendetected in post-operative cartilage tissue, and diseased areas aresmoothed without further evidence of fibrillation. In addition, thebipolar configuration of the present invention controls the flow ofcurrent to the immediate region around the distal end of the probe,which minimizes tissue necrosis and the conduction of current throughthe patient. The residual heat from the electrical energy also providessimultaneous hemostasis of severed blood vessels, which increasesvisualization of the surgical field for the surgeon, and improvesrecovery time for the patient. The techniques of the present inventionproduce significantly less thermal energy than many conventionaltechniques, such as lasers and conventional RF devices, which reducescollateral tissue damage and minimizes pain and postoperative scarring.Patients generally experience less pain and swelling, and consequentlyachieve their range of motion earlier. A more complete description ofexemplary systems and methods for treating articular cartilage can befound in co-pending commonly assigned U.S. patent application Ser. No.09/183,838, filed Oct. 30, 1998 and Ser. No. 09/177,861, filed Oct. 23,1998, (Attorney Docket Nos. A-13 and A-2-4, respectively), the completedisclosures of which are incorporated herein by reference.

[0261] In another aspect, the present invention provides anelectrosurgical probe having at least one active loop electrode forresecting and ablating tissue. In comparison to the planar electrodes,ball electrodes, or the like, the active loop electrodes provide agreater current concentration to the tissue at the target site. Thegreater current concentration can be used to aggressively create aplasma within the electrically conductive fluid, and hence a moreefficient resection of the tissue at the target site. In use, the loopelectrode(s) are typically employed to ablate tissue using theCoblation® mechanisms as described above. Voltage is applied between theactive loop electrodes and a return electrode to volumetrically loosenfragments from the target site through molecular dissociation. Once thetissue fragments are loosened from the target site, the tissue fragmentscan be ablated in situ within the plasma (i.e., break down the tissue byprocesses including molecular dissociation or disintegration).

[0262] In some embodiments, the loop electrode(s) provide a relativelyuniform smooth cutting or ablation effect across the tissue. The loopelectrodes generally have a larger surface area exposed to electricallyconductive fluid (as compared to the smaller active electrodes describedabove), which increases the rate of ablation of tissue.

[0263] Applicants have found that the current concentrating effects ofthe loop electrodes further provide reduced current dissipation into thesurrounding tissue, and consequently improved patient comfort throughthe reduced stimulation of surrounding nerves and muscle. Preferably,the loop electrode(s) extend a sufficient distance from the electrodesupport member to achieve current concentration and an improved ablationrate while simultaneously reducing current dissipation into thesurrounding medium (which can cause undesirable muscle stimulation,nerve stimulation, or thermal damage to surrounding or underlyingtissue). In an exemplary embodiment, the loop electrode has a lengthfrom one end to the other end of about 0.5 mm to 20 mm, usually about 1mm to 8 mm. The loop electrode usually extends about 0.25 mm to 10 mmfrom the distal end of the support member, preferably about 1 mm to 4mm.

[0264] The loop electrode(s) may have a variety of cross-sectionalshapes. Electrode shapes according to the present invention can includethe use of formed wire (e.g., by drawing round wire through a shapingdie) to form electrodes with a variety of cross-sectional shapes, suchas square, rectangular, L or V shaped, or the like. Electrode edges mayalso be created by removing a portion of the elongate metal electrode toreshape the cross-section. For example, material can be removed alongthe length of a solid or hollow wire electrode to form D or C shapedwires, respectively, with edges facing in the cutting direction.Alternatively, material can be removed at closely spaced intervals alongthe electrode length to form transverse grooves, slots, threads or thelike along the electrodes.

[0265] In yet another aspect, the present invention provides anelectrosurgical probe having an aspiration lumen with an opening that isspaced proximally from the active electrodes. Applicants have found thatby spacing the suction lumen opening proximal of the active electrodesthat a more aggressive plasma can be created. In use, the saline isdelivered to the target site and allowed to remain in contact with theelectrodes and tissue for a longer period of time. By increasing thedistance between the aspiration lumen and the conductive fluid, thedwell time of the conductive fluid is increased and the plasma can beaggressively created. Advantageously, by moving the aspiration lumen outof the target area, the suction will primarily aspirate blood and gasbubbles from the target site, while leaving the conductive fluid in thetarget area. Consequently, less conductive fluid and tissue fragmentsare aspirated from the target site and less clogging of the aspirationlumen occurs.

[0266] In a further aspect, the present invent provides anelectrosurgical probe having a conductive fluid delivery lumen that hasat least one distal opening positioned at least partially around theactive electrodes. The configuration of the openings can be completelyaround the active electrodes (e.g., 0 configuration or annular shaped)or partially around the active electrodes (e.g., U configuration or Cconfiguration) such that delivery of the conductive fluid immerses theactive electrodes with conductive fluid during the ablation or resectionprocedure. Because the conductive fluid can be delivered from aplurality of directions, the dwell time of the conductive fluid isincreased, and consequently the creation of the plasma can be improved.

[0267] In a preferred embodiment, the conductive fluid lumen comprises aplurality of openings that are positioned so as to substantiallysurround the active electrode array. As above, by “substantiallysurround”, is meant that the openings are at least partially around theactive electrodes. In some configurations, the openings will be equallyspaced around the active electrodes. However, it will be appreciatedthat in other alternative embodiments, the openings will only partiallysurround the active electrodes or can be unevenly spaced about theactive electrodes.

[0268] With reference to FIGS. 32-45 there follows a description of anelectrosurgical probe 1400 including a resection unit 1406, according tovarious embodiments of the instant invention. Probe 1400 is adapted foraggressive ablation, for resection, or for combined ablation andresection of tissue. Probe 1400 may be used in a broad range of surgicalprocedures including, without limitation, those listed or describedhereinabove with reference to the apparatus of FIGS. 1-31. In someembodiments, resection unit 1406 may be used to resect tissue bymechanical abrasion, cutting, or severing of tissue. In someembodiments, resection unit 1406 may be used to ablate tissue, e.g., viaa Coblation® (cool ablation) mechanism. The Coblation® mechanism hasbeen described hereinabove. Briefly, and without being bound by theory,Coblation® involves the localized generation of a plasma by theapplication of a high frequency voltage between at least one activeelectrode and a return electrode in the presence of an electricallyconductive fluid. The plasma thus generated causes the breakdown oftissues, e.g., via molecular dissociation, to form low molecular weightablation by-products. Such low molecular weight ablation by-products maybe easily removed from a target site, e.g., via aspiration. Coblation®allows the controlled removal of tissue, in which both the quantity andquality of tissue removed can be accurately determined. In someembodiments, resection unit 1406 may be used for combined resection andablation: to resect tissue by application of a mechanical force to thetissue and, concurrently therewith, to electrically ablate (“Coblate”)the tissue contacted by resection unit 1406. Applicants have found thata combination of mechanical resection and electrical ablation byresection unit 1406 provides advantageous tissue removal, as comparedwith mechanical resection or electrical ablation alone. Advantages oftissue removal by combined resection and ablation by resection unit 1406include a more rapid and aggressive tissue removal, as compared withablation alone; and a more controlled and less traumatic tissue removal,as compared with mechanical resection alone.

[0269]FIG. 32 shows probe 1400 including a shaft 1402 affixed at shaftproximal end portion 1402 b to a handle 1404. Resection unit 1406 isdisposed on shaft distal end portion 1402 a. Although FIG. 32 shows onlya single resection unit 1406 on shaft 1402, certain embodiments of theinstant invention may include a plurality of resection units 1406 whichmay be alike or dissimilar in various respects (for example, the sizeand shape of electrode support 1408, and the number, arrangement, andtype of resection electrodes 1410) (FIG. 33). In the embodiment of FIG.32, a return electrode 1420 is located at shaft distal end portion 1402a. Return electrode 1420 may be in the form of an annular band.Resection unit 1406 is shown in FIG. 32 as being arranged within, orsurrounded by, return electrode 1420. In other embodiments, resectionunit 1406 may be arranged adjacent to return electrode 1420. Under theinvention, shaft 1402 may be provided in a range of different lengthsand diameters. Preferably, shaft 1402 has a length in the range of fromabout 5 cm to about 30 cm; more preferably in the range of from about 10cm to about 25 cm. Preferably, shaft 1402 has a diameter in the range offrom about 1 mm to about 20 mm; more preferably in the range of fromabout 2 mm to about 10 mm.

[0270]FIG. 33 schematically represents resection unit 1406 of probe1400, wherein resection unit 1406 includes a resection electrode 1410 ona resection electrode support member 1408. In FIG. 33 resectionelectrode 1410 is represented as a single “box” located within support1408, however, other arrangements and numbers of resection electrode1410 are contemplated and are within the scope of the invention (see,for example, FIGS. 36A-F, FIGS. 41A-C). Resection electrode support 1408may comprise an electrically insulating, and durable or refractorymaterial, such as a glass, a ceramic, a silicone rubber, a polyurethane,a urethane, a polyimide, silicon nitride, teflon, or alumina, and thelike. Resection electrode support 1408 is shown in FIG. 33 as beingsubstantially square in outline, however, a broad range of other shapesare also possible. The size of resection electrode support 1408 maydepend on a number of factors, including the diameter or width of shaft1402. In one embodiment, support 1408 may be mounted laterally on shaft1402 as an annular band, i.e., support 1408 may completely encircleshaft 1402. Typically support 1408 represents or occupies from about 2%to 100% of the circumference of shaft 1402. More typically, support 1408occupies from about 50% to 80% of the circumference of shaft 1402, mosttypically from about 10% to 50% of the circumference of shaft 1402. Inembodiments wherein support 1408 is mounted terminally on shaft 1402,support 1408 typically occupies from about 5% to 100% of thecross-sectional area of shaft 1402, more typically from about 10% to 95%of the cross-sectional area of shaft 1402.

[0271] FIGS. 34A-D each show an electrosurgical probe 1400, according tocertain embodiments of the invention. Probe 1400 is depicted in FIGS.34A-D as being linear, however, according to various embodiments of theinvention, shaft 1402 may include one or more curves or bends therein(see, for example, FIG. 43B). Resection electrodes 1410 are omitted fromFIGS. 34A-D for the sake of clarity. However, as described elsewhereherein, each resection unit 1406 includes at least one resectionelectrode 1410 (see, for example, FIGS. 36A-F, 38A-D, 41A-C).

[0272] With reference to FIG. 34A, probe 1400 includes a fluid deliverytube 1434, and a fluid delivery port 1430 located distal to resectionunit 1406 on shaft distal end portion 1402 a. Fluid delivery port 1430is coupled to fluid delivery tube 1434 via a fluid delivery lumen 1432(FIG. 35B). Fluid delivery tube 1434 is, in turn, coupled to a source ofan electrically conductive fluid (see, e.g., FIG. 7). Fluid deliveryport 1430 is adapted to provide a quantity of an electrically conductivefluid to shaft distal end portion 1402 a during a procedure, as isdescribed elsewhere herein in enabling detail.

[0273]FIG. 34B shows probe 1400 including an aspiration tube 1444 and anaspiration port 1440 located proximal to resection unit 1406. In theembodiment depicted in FIG. 34B, aspiration tube 1444 is shown as beingconnected to probe 1400 at shaft proximal end 1402 b, however otherarrangements for coupling aspiration tube 1444 to probe 1400 arepossible under the invention. FIG. 34C shows probe 1400 including bothan aspiration tube 1444 and a fluid delivery tube 1434; and both a fluiddelivery port 1430 and an aspiration port 1440. Although fluid deliveryport 1430 is depicted in FIGS. 34A, 34C as a single port located distalto resection unit 1406, other arrangements of fluid delivery port(s)1430/1430′ with respect to resection unit 1406, are contemplatedaccording to various embodiments of the invention. Aspiration port 1440is located proximal to resection unit 1406. Preferably, aspiration port1440 is located a distance of at least 2 mm proximal to resection unit1406. More preferably, aspiration port 1440 is located a distance in therange of from about 4 mm to about 50 mm proximal to resection unit 1406.In one embodiment, aspiration port 1440 may have a screen (not shown) toprevent relatively large fragments of resected tissue from enteringaspiration lumen 1442 (FIG. 35A). Such a screen may serve as an activeelectrode and cause ablation of tissue fragments which contact thescreen. Alternatively, the screen may serve as a mechanical sieve orfilter to exclude entry of relatively large tissue fragments into lumen1442.

[0274]FIG. 34D shows probe 1400 in which resection unit 1406 is locatedat the distal terminus of shaft 1402. In this embodiment, returnelectrode 1420 is located at shaft distal end 1402 a, and aspirationport 1440 is located proximal to return electrode 1420. The embodimentof FIG. 34D may further include one or more fluid delivery ports 1430(see, for example, FIGS. 44A-D) for delivering an electricallyconductive fluid to, at least, resection unit 1406. In certainembodiments, fluid delivery port(s) 1430 deliver a quantity of anelectrically conductive fluid to shaft distal end 1402 a sufficient toimmerse resection unit 1406 and return electrode 1420. In someembodiments, fluid delivery port(s) 1430 deliver a quantity of anelectrically conductive fluid from shaft distal end 1402 a sufficient toimmerse the tissue at a site targeted for ablation and/or resection.

[0275]FIG. 35A shows electrosurgical probe 1400 including resection unit1406 and aspiration port 1440 proximal to resection unit 1406, accordingto one embodiment of the invention. Aspiration port 1440 is coupled toaspiration tube 1444 via an aspiration lumen 1442. Aspiration tube 1444may be coupled to a vacuum source, as is well known in the art.Aspiration lumen 1442 serves as a conduit for removal of unwantedmaterials (e.g., excess fluids and resected tissue fragments) from thesurgical field or target site of an ablation and/or resection procedure,essentially as described hereinabove with reference to other embodimentsof an electrosurgical probe. The embodiment of FIG. 35A may furtherinclude a fluid delivery device (see, for example, FIG. 35B).

[0276]FIG. 35B shows electrosurgical probe 1400 including resection unit1406 and fluid delivery port 1430 located distal to resection unit 1406,according to one embodiment of the invention. Fluid delivery port 1430is coupled to fluid delivery tube 1434 via a fluid delivery lumen 1432.Fluid delivery lumen 1432 serves as a conduit for providing a quantityof an electrically conductive fluid to resection unit 1406 and/or thetarget site of an ablation and resection procedure. The embodiment-ofFIG. 35B may further include an aspiration device (see, for example,FIG. 35A). In the embodiment of FIG. 35B, tube 1434 is coupled to probe1400 at handle 1404, however other arrangements for coupling tube 1434to probe 1400 are also within the scope of the invention.

[0277] FIGS. 36A-F each show a resection unit 1406 a-f as seen in planview, wherein each resection unit 1406 a-f includes a resectionelectrode support 1408 and at least one resection electrode head 1412,according to various embodiments of the invention. Each resectionelectrode 1410 (e.g., FIG. 33), may have a single terminal or resectionelectrode head 1412, such that each resection electrode head 1412 isindependently coupled to a power supply (e.g., power supply 428 of FIG.7). Alternatively, each resection electrode 1410 may have a plurality ofterminals or resection electrode heads 1412. Each resection electrode1410 may be coupled to a power supply unit (not shown in FIGS. 36A-F)via a connection block and connector cable, essentially as describedhereinabove (e.g., with reference to FIGS. 7 & 10).

[0278]FIG. 36A indicates the longitudinal axis 1406′ of resection units1406 a-f, as well as electrode support distal end 1408 a (indication oflongitudinal axis 1406′ and support distal end 1408 a are omitted fromFIGS. 36B-F for the sake of clarity, however the orientation ofresection units 1406 b-f is the same as that of resection unit 1406 a).In each of FIGS. 36A-F, resection electrode heads 1412 are depicted ashaving an elongated, substantially rectangular shape in plan view.However, other shapes and arrangements for resection electrode heads1412 are also within the scope of the invention.

[0279] FIGS. 36A-F show just some of the arrangements of resectionelectrode head(s) 1412 on each resection electrode support 1408,according to various embodiments. Briefly, FIG. 36A shows a singleresection electrode head 1412 located substantially centrally withinsupport 1408 and aligned approximately perpendicular to longitudinalaxis 1406′. FIG. 36B shows a plurality of resection electrode heads 1412arranged substantially parallel to each other and aligned substantiallyperpendicular to axis 1406′. FIG. 36C shows a plurality of resectionelectrode heads 1412 arranged substantially parallel to each other andaligned substantially perpendicular to axis 1406′, and an additionalresection electrode head 1412 arranged substantially parallel to axis1406′. FIG. 36D shows a plurality of resection electrode heads 1412arranged substantially parallel to each other and aligned at an angleintermediate between parallel to axis 1406′ and perpendicular to axis1406′. FIG. 36E shows a plurality of resection electrode heads 1412including a first substantially parallel array 1412 a aligned at a firstangle with respect to axis 1406′ and a second substantially parallelarray 1412 b aligned at a second angle with respect to axis 1406′. FIG.36F shows a plurality of resection electrode heads 1412 having anarrangement similar to that described for FIG. 36E, wherein resectionelectrode heads 1412 are of different sizes.

[0280]FIG. 37 illustrates an angle at which a resection electrode head1412 may be arranged on electrode support 1408 with respect to thelongitudinal axis 1406′ of resection unit 1406. According to certainembodiments, resection electrode heads 1412 may be arranged on electrodesupport 1408 at an angle in the range of from 0° to about 175° withrespect to longitudinal axis 1406′. In embodiments having first andsecond parallel arrays of resection electrode heads 1412, e.g., FIG.36E, first array 1412 a is preferably arranged at an angle α in therange of from about 90° to 170°, and more preferably from about 105° to165°. Second array 1412 b is preferably arranged at an angle β in therange of from about 100 to 90°, and more preferably from about 15° to75°.

[0281]FIG. 38A shows in plan view a resection electrode support 1408arranged on shaft distal end portion 1402 a, wherein electrode support1408 includes resection electrode head 1412. FIGS. 38B-D each show aprofile of a resection electrode head 1412 on an electrode support 1408as seen along the line 38B-D of FIG. 38A. From an examination of FIGS.38B-D it can be readily seen that, according to certain embodiments ofthe invention, resection electrode head 1412 may protrude a significantdistance from the external surface of shaft 1402. Typically, eachresection electrode head 1412 protrudes from resection electrode support1408 by a distance in the range of from about 0.1 to 20 mm, andpreferably by a distance in the range of from about 0.2 to 10 mm.Resection electrode head 1412 may have a profile which is substantiallysquare or rectangular; arched or semi-circular; or angular and pointed,as represented by FIGS. 38B-D, respectively. Other profiles and shapesfor resection electrode head 1412 are also within the scope of theinvention. Only one resection electrode head 1412 is depicted perelectrode support 1408 in FIGS. 38A-D. However, according to theinvention, each electrode support 1408 may have a plurality of resectionelectrode heads 1412 arranged thereon in a variety of arrangements (see,e.g., FIGS. 36A-F).

[0282] In the embodiments of FIGS. 38B-D, each electrode head 1412 is inthe form of a filament or wire of electrically conductive material. Inone embodiment, the filament or wire comprises a metal. Such a metal ispreferably a durable, corrosion resistant metal. Suitable metals forconstruction of resection electrode head 1412 include, withoutlimitation, tungsten, stainless steel alloys, platinum or its alloys,titanium or its alloys, molybdenum or its alloys, and nickel or itsalloys. In embodiments wherein each electrode head 1412 is in the formof a filament or wire, the diameter of the wire is preferably in therange of from about 0.05 mm to about 5 mm, more preferably in the rangeof from about 0.1 to about 2 mm.

[0283] FIGS. 39A-I each show a cross-section of the filament or wire ofresection electrode head 1412 as seen, for example, along the lines39A-I of FIG. 38B. Evidently, a variety of different cross-sectionalshapes for resection electrode head 1412 are possible. For example,resection electrode head 1412 may be substantially round or circular,substantially square, or substantially triangular in cross-section, asdepicted in FIGS. 39A-C, respectively. Resection electrode head 1412 mayhave a cross-section having at least one curved side. For example, head1412 d of FIG. 39D has two substantially parallel sides and two concavesides. Head 1412 e of FIG. 39E has four concave sides forming fourcusps, while head 1412 f (FIG. 39F) includes three concave sides formingthree cusps. FIGS. 39G-I each depict a cross-section of a wire orfilament having serrations on at least one side thereof. Resectionelectrode head 1412 g comprises a filament having a substantiallycircular cross-section, wherein the circumference of the filament isserrated. In another embodiment (not shown) a selected portion of thecircumference of a substantially round filament may be serrated.Resection electrode head 1412 h (FIG. 39H) comprises a filament having asubstantially square cross-section, wherein a leading or cutting edgeportion 1413 h of the filament is serrated. FIG. 391 shows a head 1412 icomprising a filament of an electrically conductive material having asubstantially crescent-shaped or semi-circular cross-sectional shape,wherein cutting edge portion 1413 i is serrated. In addition, othercross-sectional shapes for electrode head 1412 are contemplated and arewithin the scope of the invention. Preferably, the cross-sectional shapeand other features of resection electrode head 1412 promote high currentdensities in the vicinity of resection electrode head 1412 followingapplication of a high frequency voltage to resection electrode head1412. More preferably, the cross-sectional shape and other features ofresection electrode head 1412 promote high current densities in thevicinity of a leading or cutting edge, e.g., edge 1413 h, 1413 i, ofresection electrode head 1412 following application of a high frequencyvoltage to resection electrode head 1412. As noted previously, highcurrent densities promote generation of a plasma in the presence of anelectrically conductive fluid, and the plasma in turn efficientlyablates tissue via the Coblation® procedure or mechanism. Preferably,the cross-sectional shape and other features of resection electrode head1412 are also adapted for maintenance of the plasma in the presence of astream of fluid passing over resection electrode head 1412. In oneembodiment, the cross-sectional shape and other features of resectionelectrode head 1412 are also adapted for the efficient mechanicalresection, abrading, or severing of, at least, soft tissue (such asskeletal muscle, skin, cartilage, etc.).

[0284] In one embodiment a cutting edge, e.g., edge 1413 h, 1413 i, isadapted for both ablating and resecting tissue. Depending on theembodiment, cutting edge 1413 h, 1413 i may be oriented, or point, invarious directions relative to the longitudinal axis of shaft 1402. Forexample, depending on the particular embodiment of probe 1400, and onthe particular surgical procedure(s) for which embodiments of probe 1400are designed to perform, cutting edge 1413 h, 1413 i maybe orienteddistally, proximally, or laterally.

[0285]FIG. 40 shows a cross-section of a resection electrode head 1412,according to another embodiment of the invention, wherein head 1412includes a cutting edge 1413, and an insulating layer 1414 disposed on acovered portion of head 1412, and wherein cutting edge 1413 is free frominsulating layer 1414. Cutting edge 1413 promotes high current densitiesin a region between resection electrode head 1412 and the target siteupon application of a high frequency voltage to resection electrode head1412. At the same time, insulating layer 1414 reduces undesirablecurrent flow into tissue or surrounding electrically conducting liquidsfrom covered (insulated) portion of resection electrode head 1412. Theapplication or deposition of insulating layer 1414 to resectionelectrode head 1412 may be achieved by for example, thin-film depositionof an insulating material using evaporative or sputtering techniques,well known in the art. Insulating layer 1414 provides an electricallyinsulated non-active portion of resection electrode head 1412, therebyallowing the surgeon to selectively resect and/or ablate tissue, whileminimizing necrosis or ablation of surrounding non-target tissue orother body structures.

[0286]FIG. 41A illustrates a distal end of an electrosurgical probeshowing in plan view resection electrode support 1408 including aplurality of resection electrode heads 1412′, according to anotherembodiment of the invention. In contrast to resection electrode heads1412 described hereinabove, each resection electrode head 1412′ in theembodiment of FIGS. 41A-C is in the form of a blade. In one embodiment,each resection electrode head 1412′ may have a covered portion having aninsulating layer thereon (analogous to insulating layer 1414 ofresection electrode head 1412 of FIG. 40). Resection electrode heads1412′ are depicted in FIG. 41A as being arranged in a pair of angledparallel electrode head arrays. However, other arrangements forresection electrode heads 1412′ are within the scope of the invention.FIG. 41B shows resection electrode heads 1412′ as seen along the lines41B-41B of FIG. 41A. Each resection electrode head 1412′ may include acutting edge 1413′ adapted for promoting high current density in thevicinity of each resection electrode head 1412′ upon application of ahigh frequency voltage thereto. In one embodiment, cutting edge 1413′ isalso adapted for severing or mechanical resection of tissue. In oneembodiment, cutting edge 1413′ is serrated. Cutting edge 1413′ is shownin FIG. 41B as facing away from shaft distal end portion 1402 a.However, in an analogous situation to that described hereinabove withreference to FIGS. 39H-I, various embodiments of probe 1400 may havecutting edge 1413′ facing in any direction with respect to thelongitudinal axis of shaft 1402, e.g., cutting edge 1413′ may facedistally, proximally, or laterally. Thus, probe 1400 may be provided ina form suitable for performing a broad range of resection and ablationprocedures.

[0287]FIG. 41C illustrates shaft distal end 1402 a of electrosurgicalprobe 1400, taken along the lines 41C-41C of FIG. 41A, showing resectionelectrode heads 1412′ on resection electrode support 1408. From anexamination of FIGS. 41B-C it can be readily appreciated that, accordingto certain embodiments of the invention, resection electrode heads 1412′may protrude a significant distance from the external surface of shaft1402. Typically, each resection electrode head 1412′ protrudes fromresection electrode support 1408 by a distance in the range-of fromabout 0.1 to 20 mm, and preferably by a distance in the range of fromabout 0.2 to 10 mm. Each resection electrode head 1412′ may comprise ametal blade, wherein the metal blade comprises a metal such as,stainless steel, tungsten, platinum, titanium, molybdenum, nickel ortheir alloys, and the like.

[0288]FIG. 42A is a sectional view of shaft 1402 including distal endportion 1402 a. Shaft 1402 includes resection unit 1406 and fluiddelivery port 1430 for supplying electrically conductive fluid toresection unit 1406 via fluid delivery lumen 1432. A plurality ofaspiration ports 1440 are located proximal to resection unit 1406.Aspiration ports 1440 lead to aspiration lumen 1442. Applicants havedetermined that positioning aspiration ports somewhat distant fromresection unit 1406 and delivery port 1430, the dwell time of theelectrically conductive fluid is increased, and a plasma can be createdmore aggressively and consistently. Advantageously, by moving theaspiration ports somewhat distant from the target site, suction willprimarily aspirate excess or unwanted fluids (e.g., tissue fluids,blood, etc.) and gaseous ablation by-products from the target site,while the electrically conductive fluid, such as isotonic saline,remains at the target site. Consequently, less conductive fluid andtissue fragments are aspirated from the target site, and entry ofresected tissue fragments into aspiration lumen 1442 is less likely tooccur.

[0289] In the embodiments of FIGS. 42A-B, aspiration lumen 1442 includesat least one digestion electrode 1450. More preferably, aspiration lumen1442 includes a plurality of digestion electrodes 1450. Each digestionelectrode 1450 serves as an active (ablation) electrode and is coupledto a high frequency power supply (e.g. power supply 428 of FIG. 7). Eachdigestion electrode 1450 is adapted for rapidly breaking down any tissuefragments that may be drawn into aspiration lumen 1442 during aresection and ablation procedure. In this manner, lumen 1442 remainsfree from blockage, and allows a surgical procedure to be completedconveniently and efficiently without interruption to either unblocklumen 1442 or to replace probe 1400. The shape, arrangement, size, andnumber, of digestion electrodes 1450 is to some extent a matter ofdesign choice. Preferably, each digestion electrode 1450 is adapted toprovide a high current density upon application thereto of a highfrequency voltage, thereby promoting rapid and efficient ablation ofresected tissue fragments.

[0290] In one embodiment, a plurality of digestion electrodes 1450 of asuitable shape and size may be arranged within aspiration lumen 1442such that digestion electrodes 1450 at least partially overlap orinterweave. Such overlapping digestion electrodes 1450 may act, at leastto some extent, as a screen to mechanically restrain tissue fragmentsthereat. While tissue fragments are restrained against one or moredigestion electrodes 1450, the latter may efficiently ablate the formerto yield low molecular weight ablation by-products which readily passthrough lumen 1442 in the aspiration stream. FIG. 42B illustrates intransverse section shaft 1402 taken along the lines 42B-42B of FIG. 42A,and showing fluid delivery lumen 1432 and aspiration lumen 1442, thelatter having digestion electrodes 1450 arranged therein. In thisembodiment, digestion electrodes 1450 are shown as having pointedsurfaces, such as are known to promote high current densities thereat,and digestion electrodes 1450 at least partially interweave with eachother.

[0291] FIGS. 43A-D are side views of shaft distal end portion 1402 a ofan electrosurgical probe 1400. FIG. 43A shows resection electrodesupport 1408 disposed laterally on a linear or substantially linearshaft distal end 1402 a. FIG. 43B shows resection electrode support 1408disposed on the terminus of shaft 1402, wherein shaft distal end 1402 aincludes a bend or curve. In the embodiments of FIGS. 43A, 43B,electrode support 1408 protrudes from an external surface of shaftdistal end portion 1402 a. Typically, electrode support 1408 protrudes adistance in the range of from about 0 (zero) to about 20 mm from theexternal surface of shaft 1402. Each resection electrode support 1408 ofthe invention includes at least one resection electrode terminal or head1412/1412′. Each resection electrode head 1412/1412′ is coupled, e.g.via a connection block and connecting cable, to a high frequency powersupply unit, essentially as described hereinabove. However, for the sakeof clarity, resection electrode head(s) 1412/1412′ are omitted fromFIGS. 43A-D.

[0292]FIG. 43C shows shaft 1402 having resection electrode support 1408countersunk or recessed within shaft distal end 1402 a. In thisembodiment, an external surface of resection electrode support 1408 maybe aligned, or flush, with an external surface of shaft 1402. In thisembodiment, resection electrode heads 1412/1412′ (FIGS. 38B-D, 41A-C)may protrude from the external surface of shaft distal end 1402 a tovarious extents, as described hereinabove. FIG. 43D shows a shaft distalend portion 1402 having a depression or cavity 1416 therein. In thisembodiment, resection electrode support 1408 is housed within cavity1416. In this embodiment, resection electrode heads 1412/1412′ may, ormay not, extend above cavity 1416 and from the shaft external surface.In this embodiment the extent, if any, to which resection electrodeheads 1412/1412′ extend above cavity 1416 is determined by the depth ofcavity 1416, as well as by the height of resection electrode support1408, and the height of resection electrode heads 1412/1412′. Theembodiment of FIG. 43D serves to isolate non-target tissue fromresection electrode heads 1412/1412′, thereby minimizing collateraldamage to such tissue during a resection and ablation procedure.

[0293] Referring now to FIGS. 44A-D, a fluid delivery device fordelivering an electrically conductive fluid to resection unit 1406 or totissue at a target site can include a single fluid delivery port 1430(e.g., FIG. 34A) or a plurality of ports 1430. In exemplary embodimentsof probe 1400, ports 1430 are disposed around a perimeter of resectionunit 1406, and are positioned to deliver the conductive fluid toresection electrode head(s) 1412/1412′. As shown in FIG. 44A, aplurality of ports 1430 may be arranged around a distal portion ofresection unit 1406. In the embodiment of FIG. 44B a plurality of ports1430 are arranged around the entire perimeter of resection unit 1406.The arrows shown in FIG. 44B indicate a direction in which anelectrically conductive fluid may be delivered from the plurality offluid delivery ports 1430. In one embodiment, fluid delivery ports 1430are rounded or substantially circular in outline.

[0294] As shown in FIG. 44C, a fluid delivery port 1430′ may be in theform of an elongated opening or slit extending around a distal portionof resection unit 1406. In the embodiment of FIG. 44D port 1430′ is inthe form of a single slit extending around the perimeter of resectionunit 1406. In each embodiment (FIGS. 44A-D), delivery ports 1430/1430′preferably deliver electrically conductive fluid in the direction ofresection unit 1406. The amount of electrically conductive fluiddelivered to resection unit 1406, and the timing or periodicity of suchfluid delivery, may be controlled by an operator (surgeon). In oneembodiment, the amount of electrically conductive fluid delivered toresection unit 1406 is sufficient to, at least transiently, immerseresection electrode heads 1412/1412′ in the electrically conductivefluid.

[0295]FIG. 45 shows a shaft distal end portion 1402 a of shaft 1402,according to one embodiment of the invention. In this embodiment,resection unit 1406/resection electrode support 1408 is disposed onreturn electrode 1420, wherein return electrode 1420 comprises anexposed region of shaft 1402. By “exposed region” is meant a region ofshaft distal end portion 1402 a which is not covered by an insulatingsleeve or sheath 1460. Insulating sleeve 1460 may comprise a layer orcoating of a flexible insulating material, such as various plastics(e.g., a polyimide or polytetrafluoroethylene, and the like) as is wellknown in the art. In this embodiment, a plurality of fluid deliveryports 1430 are positioned within return electrode 1420 such that whenthe electrically conductive fluid contacts resection electrode heads1412/1412′ on resection electrode support 1408, an electrical circuit,or current flow path, is completed. A plurality of aspiration ports 1440are spaced proximally from resection electrode support 1408 for removingunwanted fluids, such as ablation by-products, from the vicinity ofresection unit 1406. Resection electrode support 1408 may besubstantially square, rectangular, oval, circular, etc. Typically,resection electrode support 1408 has a dimension in the longitudinaldirection of the shaft (i.e., a length) in the range of from about 1 mmto about 20 mm, more typically in the range of from about 2 mm to about10 mm.

[0296] Referring now to FIG. 46, a surgical kit 1500 for resectingand/or ablating tissue according to the invention will now be described.FIG. 46 schematically represents surgical kit 1500 includingelectrosurgical probe 1400, a package 1502 for housing probe 1400, asurgical instrument 1504, and an instructions for use 1506. Instructionsfor use 1506 include instructions for using probe 1400 in conjunctionwith apparatus ancillary to probe 1400, such as power supply 428 (FIG.7). Package 1502 may comprise any suitable package, such as a box,carton, etc. In an exemplary embodiment, package 1502 includes a sterilewrap or wrapping 1504 for maintaining probe 1400 under asepticconditions prior to performing a surgical procedure.

[0297] An electrosurgical probe 1400 of kit 1500 may comprise any of theembodiments described hereinabove. For example, probe 1400 of kit 1500may include shaft 1402 having at least one resection electrode 1410 atshaft distal end 1402 a, and at least one connector (not shown)extending from the at least one resection electrode 1410 to shaftproximal end 1402 b for coupling resection electrode 1410 to a powersupply. Probe 1400 and kit 1500 are disposable after a single procedure.Probe 1400 may or may not include a return electrode 1420.

[0298] Instructions for use 1506 generally includes, without limitation,instructions for performing the steps of: adjusting a voltage level of ahigh frequency power supply to effect resection and/or ablation oftissue at the target site; connecting probe 1400 to the high frequencypower supply; positioning shaft distal end 1402 a within an electricallyconductive fluid at or near the tissue at the target site; andactivating the power supply to effect resection and/or ablation of thetissue at the target site. An appropriate voltage level of the powersupply is usually in the range of from about 40 to 400 volts RMS foroperating frequencies of about 100 to 200 kHz. Instructions 1506 mayfurther include instruction for advancing shaft 1402 towards the tissueat the target site, and for moving shaft distal end portion 1402 a inrelation to the tissue. Such movement may be performed with or withoutthe exertion of a certain mechanical force on the target tissue viaresection unit 1406, depending on parameters such as the nature of theprocedure to be performed, the type of tissue at the target site, therate at which the tissue is to be removed, and the particular design orembodiment of probe 1400/resection unit 1406.

[0299] FIGS. 47A-B schematically represent a method of performing aresection and ablation electrosurgical procedure, according to anotherembodiment of the invention, wherein step 1600 (FIG. 47A) involvesproviding an electrosurgical probe having a resection unit. The probeprovided in step 1600 includes a shaft distal end, wherein the resectionunit is disposed at the shaft distal end, either laterally orterminally. The resection unit includes an electrode support comprisingan insulating material and at least one resection electrode headarranged on the electrode support. Step 1602 involves adjusting avoltage level of a power supply, wherein the power supply is capable ofproviding a high frequency voltage of a selected voltage level andfrequency. The voltage selected is typically between about 5 kHz and 20MHz, essentially as described hereinabove. The RMS voltage will usuallybe in the range of from about 5 volts to 1000 volts, and thepeak-to-peak voltage will be in the range of from about 10 to 2000volts, again as described hereinabove. The actual or preferred voltagewill depend on a number of factors, including the number and size ofresection electrodes comprising the resection unit.

[0300] Step 1604 involves coupling the probe to the power supply unit.Step 1606 involves advancing the resection unit towards tissue at atarget site whence tissue is to be removed. In optional step 1608, aquantity of an electrically conductive fluid may be applied to theresection unit and/or to the target site. For performance of a resectionand ablation procedure in a dry field, optional step 1608 is typicallyincluded in the procedure. Step 1608 may involve the application of aquantity of an electrically conductive fluid, such as isotonic saline,to the target site. The quantity of an electrically conductive fluid maybe controlled by the operator of the probe. The quantity of anelectrically conductive fluid applied in step 1608 may be sufficient tocompletely immerse the resection unit and/or to completely immerse thetissue at the target site. Step 1610 involves applying a high frequencyvoltage to the resection unit via the power supply unit. Step 1612involves contacting the tissue at the target site with the resectionunit.

[0301] With reference to FIG. 47B, optional step 1614 involves exertingpressure on the tissue at the target site by applying a force to theprobe, while the resection unit is in contact with the tissue at thetarget site, in order to effect resection of tissue. Typically, such aforce is applied manually by the operator (surgeon), although mechanicalapplication of a force to the probe, e.g., by a robotic arm undercomputer control, is also possible. The amount of any force applied inoptional step 1614 will depend on factors such as the nature of thetissue to be removed, the design or embodiment of the probe, and theamount of tissue to be resected. For example, in the absence of anymechanical force applied to the tissue, tissue removal from the targetsite is primarily or solely by ablation. On the other hand, with theelectrical power turned off, either transiently or for all or a portionof a procedure, the probe may be used for mechanical resection oftissue. Typically, however, the probe is used for the concurrentelectrical ablation and mechanical resection of tissue.

[0302] Step 1616 involves moving the resection unit of the probe withrespect to the tissue at the target site. Typically, step 1616 involvesmoving the resection unit and the at least one resection electrode headin a direction substantially perpendicular to a direction of anypressure exerted in step 1614, or in a direction substantially parallelto a surface of the tissue at the target site. Typically, step 1616 isperformed concurrently with one or more of steps 1608 through 1614. Inone embodiment, step 1616 involves repeatedly moving the resection unitwith respect to the tissue at the target site until an appropriatequantity of tissue has been removed from the target site. Typically, aportion of the tissue removed from the target site is in the form ofresected tissue fragments. Step 1618 involves aspirating the resectedtissue fragments from the target site via at least one aspiration porton the shaft, wherein the at least one aspiration port is coupled to anaspiration lumen. In one embodiment, the probe includes at least onedigestion electrode capable of aggressively ablating resected tissuefragments. Step 1620 involves ablating resected tissue fragments withthe at least one digestion electrode. In one embodiment, the at leastone digestion electrode is arranged within the aspiration lumen, and theresected tissue fragments are ablated within the aspiration lumen.

[0303]FIG. 48 schematically represents a method of making a resectionand ablation electrosurgical probe, according to the invention, whereinstep 1700 involves providing a shaft having a resection unit. The shaftprovided in step 1700 includes a shaft proximal end and a shaft distalend, wherein the resection unit is disposed at the shaft distal end,either laterally or terminally. In one embodiment, the shaft comprisesan electrically conductive lightweight metal cylinder. The resectionunit includes an electrode support comprising an insulating material andat least one resection electrode arranged on the electrode support. Eachresection electrode includes a resection electrode head. Each resectionelectrode head typically comprises a wire, filament, or blade of a hardor rigid, electrically conductive solid material, such as tungsten,stainless steel alloys, platinum or its alloys, titanium or its alloys,molybdenum or its alloys, nickel or its alloys, and the like.

[0304] Typically, the shaft provided in step 1700 further includes atleast one digestion electrode capable of aggressively ablating tissuefragments. In one embodiment, the at least one digestion electrode isarranged within the aspiration lumen. Each digestion electrode typicallycomprises an electrically conductive metal, such as tungsten, stainlesssteel alloys, platinum or its alloys, titanium or its alloys, molybdenumor its alloys, nickel or its alloys, aluminum, gold, or copper, and thelike. Typically, the shaft provided in step 1700 further includes areturn electrode.

[0305] In one embodiment, the method includes step 1702 which involvesencasing a portion of the shaft within an insulating sleeve to providean electrically insulated proximal portion of the shaft and an exposeddistal portion of the shaft. The exposed distal portion of the shaftdefines a return electrode of the probe. The insulating sleeve typicallycomprises a substantially cylindrical length of a flexible insulatingmaterial such as polytetrafluoroethylene, a polyimide, and the like.Such flexible insulating materials are well known in the art. In oneembodiment, the resection electrode support is disposed on the returnelectrode. The resection electrode support typically comprises anelectrically insulating material such as a glass, a ceramic, a siliconerubber, a polyurethane, a urethane, a polyimide, silicon nitride,teflon, alumina, or the like. The electrode support serves toelectrically insulate the at least one resection electrode head from thereturn electrode. Step 1704 involves providing a handle having aconnection block. Step 1706 involves coupling the resection electrodesand the digestion electrodes to the connection block. The connectionblock provides a convenient mechanism by which the resection anddigestion electrodes may be coupled to a high frequency power supply.Step 1708 involves affixing the shaft proximal end to the handle.

[0306] There now follows a description, with reference to FIGS. 49-60B,of an electrosurgical probe 1800 and associated electrosurgical systemadapted for the aggressive removal of tissue during a broad range ofsurgical procedures. According to one aspect of the invention, probe1800 differs from certain other probes described hereinbelow, and fromconventional probes of the prior art, in that probe 1800 lacks adedicated or permanent return electrode. Furthermore, in use theelectrosurgical system of which probe 1800 is a part is not operated inconjunction with a non-integral return electrode (e.g., a dispersivepad). Rather, probe 1800 includes a first electrode (or electrode type)and a second electrode (or electrode type), wherein each of the firstelectrode type and the second electrode type is designed and adapted forhaving a tissue-altering effect on a target tissue. That is to say, eachof the first electrode type and the second electrode type can functionas an active electrode. Each of the first electrode type and the secondelectrode type can also function as a return electrode. In particular,the first electrode and the second electrode can alternate betweenserving as an active electrode and serving as a return electrode.Typically, when the first electrode serves as the active electrode, thesecond electrode serves as the return electrode; and when the secondelectrode serves as the active electrode, the first electrode serves asthe return electrode. In use, the first electrode and the secondelectrode are independently coupled to opposite poles of a highfrequency power supply to enable current flow therebetween. For example,the first electrode and the second electrode may be independentlycoupled to opposite poles of power supply 428 (FIG. 7), for supplyingalternating current to the first electrode and the second electrode.

[0307] Typically, the first electrode or electrode type comprises one ormore ablation electrodes 1810, and the second electrode or electrodetype comprises one or more digestion electrodes 1820 (e.g., FIG. 49).According to one embodiment, at any given time point electric power isgenerally supplied preferentially to the first electrode or to thesecond electrode. That is to say, at any given time point the highfrequency power supply alternatively supplies most of the power toeither the first electrode or to the second electrode. In this manner,at any given time point either the first electrode or the secondelectrode may receive up to about 100% of the power from the powersupply. Typically, an electrode or electrode type which receives most ofthe power from the power supply receives from about 60% to about 100% ofthe power; and more typically from about 70% to about 100% of the power.The actual percentage of power preferentially received by one of the twoelectrode types at any given time point may vary according to a numberof factors, including: the power level or setting of the power supply,the electrical impedance of any tissue in the presence of the twoelectrode types, and the geometry of the two electrode types.

[0308] Typically, when only the ablation electrode is in contact withtissue, the ablation electrode preferentially receives electric powerfrom the power supply such that the ablation electrode functions as theactive electrode and ablates tissue, e.g., at a target site targeted fortreatment. In this ablation mode, the digestion electrode normallyserves as a return electrode. Conversely, when only the digestionelectrode is in contact with tissue, the digestion electrode typicallyreceives the majority of the electric power from the power supply suchthat the digestion electrode functions as the active electrode and iscapable of ablating tissue (e.g., digesting tissue fragments resectedfrom the target site during the ablation mode). In this digestion mode,the ablation electrode normally serves as a return electrode.

[0309] Typically, when one of the two electrode types encounters tissuesuch that the milieu of that electrode type undergoes a change inelectrical impedance, while the other electrode type is not in contactwith or adjacent to tissue in this manner, the former electrode typepreferentially receives power from the power supply. Typically, theelectrode type which preferentially receives power from the power supplyfunctions as active electrode and is capable of having a tissue-alteringeffect. Usually, only one of the two electrode types can function asactive electrode during any given time period. During that given timeperiod, the other, non-active electrode functions as a return electrodeand is incapable of having a tissue-altering effect. While not beingbound by theory, Applicants believe that the preferential delivery ofpower to one electrode type in the presence of tissue, while the otherelectrode type is not in the presence of tissue, is due to theelectrical impedance of the tissue causing relatively high currentdensities to be generated at the former electrode type.

[0310] In one mode of operation, both the first and second electrodetypes may be in contact with tissue simultaneously. For example, anablation electrode of the probe may be in contact with tissue at a sitetargeted for treatment, and at the same time the digestion electrode maybe in contact with one or more fragments of tissue resected from thetarget site. If the ablation and digestion electrodes are both incontact with tissue at the same time but the electrodes have differentsurface areas, the available power may be supplied preferentially to oneof the two electrode types. In particular, by arranging for anappropriate ablation electrode:digestion electrode surface area ratio,when tissue is in contact with or in the vicinity of the digestionelectrode, the digestion electrode may receive the majority of theavailable electric power and thus function as the active electrode. Byarranging for an appropriate ablation electrode:digestion electrodesurface area ratio, a shift from the ablation electrode serving asactive electrode to the digestion electrode serving as active electrodecan be triggered by a change in electrical impedance in the vicinity ofthe digestion electrode. Such a change in electrical impedance typicallyresults from the presence of one or more tissue fragments, e.g. a tissuefragment flowing towards the digestion electrode in an aspirationstream. According to one aspect of the invention, the ablationelectrode:digestion electrode surface area ratio is in the range of fromabout 3:1 to about 1.5:1.

[0311] According to the invention, the elimination of a conventional ordedicated return electrode from probe 1800 enables the active electrode,i.e., either the ablation electrode or the digestion electrode, toreceive up to 100%, of the power or current supplied by the highfrequency power supply. For convenience, the terms ablation electrodeand digestion electrode may be used hereafter in the singular form, itbeing understood that such terms include one, or more than one, ablationelectrode; and one, or more than one, digestion electrode, respectively.Ablation electrode 1810 is capable of aggressively removing tissue froma target site by a cool ablation mechanism (Coblation®), generally asdescribed hereinabove. Typically, the temperature of tissue subjected tocool ablation according to the instant invention is in the range of fromabout 45° C. to 90° C., and more typically in the range of from about60° C. to 70° C.

[0312] According to one embodiment, ablation electrode 1810 may beregarded as a default or primary active electrode, and as a back-up orsecondary return electrode; while digestion electrode 1820 may beregarded as a default or primary return electrode and as a secondaryactive electrode. The active electrode (either electrode 1810 orelectrode 1820, depending on the mode of operation of theelectrosurgical system) generates a plasma from an electricallyconductive fluid present in the vicinity of the active electrode, andthe plasma causes breakdown of tissue in the region of the activeelectrode by molecular dissociation of tissue components to form lowmolecular weight Coblation® by-products, essentially as describedhereinabove. The return electrode completes a current flow path from theactive electrode via the electrically conductive fluid locatedtherebetween, and has no significant tissue-altering effect whileserving as the return electrode.

[0313] In one embodiment and according to one mode of operation of anelectrosurgical system of the invention, probe 1800 is configured suchthat only one of the two electrode types is in contact with tissue at atarget site. According to one aspect of the invention, probe 1800 isconfigured such that one of the two electrode types can be brought intocontact with tissue at a target site while the other of the twoelectrode types remains remote from the tissue at the target site.Typically, probe 1800 is configured such that ablation electrode 1810can be readily brought into contact with the tissue at the target site,while digestion electrode 1820 avoids contact with the tissue at thetarget site.

[0314] According to one aspect of the invention, when ablation electrode1810 is in the presence of tissue (e.g., at a target site) and in theabsence of tissue (e.g. resected tissue fragments) in the milieu ofdigestion electrode 1820, electrodes 1810, 1820 may serve as defaultactive and return electrodes, respectively. However, when tissue ispresent in the milieu of digestion electrode 1820, power from the powersupply may be switched from ablation electrode 1810 to digestionelectrode 1820, such that electrode 1820 serves as an active electrodewhile ablation electrode 1810 serves as the return electrode. In oneaspect, such an alternation, or reversal, of roles between electrodes1810, 1820 may be a transient event. For example, in the presence of aresected tissue fragment, digestion electrode 1820 may preferentiallyreceive power from the power supply and assume the role of activeelectrode, such that a plasma is generated in the vicinity of digestionelectrode 1820, and the resected tissue fragment is broken down viaCoblation® to form low molecular weight byproducts. Thereafter, in theabsence of tissue in the milieu of digestion electrode 1820, electrode1820 may rapidly revert to its role of default return electrode. At thesame time, ablation electrode 1810 reverts to its role of default activeelectrode. The respective roles of electrodes 1810 and 1820 as activeand return electrodes, respectively, may then continue until digestionelectrode 1820 again encounters tissue in its vicinity. In this manner,digestion electrode 1820 generally only receives most of the power fromthe power supply in the presence of tissue (e.g., a resected tissuefragment), while ablation electrode 1810 may preferentially receivepower from the power supply at all times other than when digestionelectrode 1820 preferentially receives power from the power supply.

[0315] While not being bound by theory, Applicants believe that thetransformation or “switch” of digestion electrode 1820, from serving asreturn electrode to serving as active electrode, may be mediated by achange in electrical impedance in the vicinity of digestion electrode1820, wherein the impedance change results from the presence of tissuein the electrically conductive fluid adjacent to electrode 1820. Again,while not being bound by theory, Applicants believe that the ratio ofthe surface area of the ablation electrode (Sa) to the surface area ofthe digestion electrode (Sd), Sa:Sd is a factor in causing electrodes1810 and 1820 to alternate between active/return electrode mode.Generally, the Sa:Sd ratio is in the range of from about 3.5:1 to about1: 1, typically in the range of from about 2.5:1 to about 1.5:1, andusually about 2:1. By selecting a suitable Sa:Sd ratio for probe 1800,as has been achieved by Applicants, the feature of alternating betweenpreferentially supplying power to ablation electrode 1810 andpreferentially supplying power to digestion electrode 1820 becomes aninherent characteristic of an electrosurgical system according to theinvention. An effective or optimum Sa:Sd ratio for bringing about ashift in preferentially supplying power to either ablation electrode1810 or digestion electrode 1820 may vary according to a number ofparameters including the volume of materials aspirated from a targetsite, and the velocity of an aspiration stream. Therefore, in someembodiments an aspiration stream control unit (not shown) may be used inconjunction with probe 1800 in order to quantitatively regulate theaspiration stream.

[0316]FIG. 49 shows a side view of an electrosurgical probe 1800 for usein conjunction with an electrosurgical system, according to oneembodiment of the invention. Probe 1800 includes a handle 1804 and ashaft 1802 having shaft distal end 1802 a and shaft proximal end 1802 b.In this embodiment, ablation electrode 1810 and digestion electrode 1820are mounted on the distal terminus 1806 of shaft 1802. However, lateralmounting of ablation electrode 1810 and digestion electrode 1820 is alsopossible under the invention. In light of the absence of a permanent ordedicated return electrode from probe 1800, shaft 1802 may comprise arigid insulating material, for example, various synthetic polymers,plastics, and the like, well known in the art. Alternatively, shaft 1802may comprise an electrically conducting solid material whose surface isentirely covered with an insulating material. Such electricallyconducting solid materials include various metals such as stainlesssteel, tungsten and its alloys, and the like. An insulating materialcovering shaft 1802 may comprise a flexible, electrically insulatingsleeve or jacket of a plastic material, such as a polyimide, and thelike. Typically, shaft 1802 has a length in the region of from about 5to 30 cm, more typically from about 7 to 25 cm, and most typically fromabout 10 to 20 cm. Generally, handle 1804 has a length in the range offrom about 2 to 10 cm.

[0317]FIG. 50A is a longitudinal section of probe 1800 including shaftdistal end 1802 a having ablation electrode 1810 and digestion electrode1820 mounted at shaft distal terminus 1806. Handle 1804 includes aconnection block 1805. Ablation electrode 1810 and digestion electrode1820 are connected to connection block 1805 via ablation electrode lead1811 and digestion electrode lead 1821, respectively. Leads 1811, 1821enable ablation electrode 1810 and digestion electrode 1820 to becoupled to a power supply independently of each other, such thatablation electrode 1810 and digestion electrode 1820 can independentlyreceive power from the power supply. Connection block 1805 provides aconvenient mechanism for coupling electrodes 1810, 1820 to the powersupply, e.g., via one or more connecting cables (see, e.g., FIG. 7).Probe 1800 of FIG. 50A also includes an aspiration device, namely aterminal aspiration port 1840, an aspiration lumen 1842 leadingproximally from port 1840, and an aspiration tube 1844 coupled to lumen1842. Tube 1844 may be coupled to a vacuum source, for applying a vacuumor partial vacuum to port 1840, and to a collection reservoir forcollecting aspirated materials, as is well known in the art.

[0318]FIG. 50B is an end view of shaft distal terminus 1806 of FIG. 50A,as seen along the lines 50B-50B of FIG. 50A. In FIG. 50B, ablationelectrode 1810 and digestion electrode 18200 are each represented as arectangular box located at approximately 12 o'clock and six o'clock,respectively, on either side of a substantially centrally locatedaspiration port 1840. However, various other shapes, number,arrangements, etc. for electrodes 1810, 1820 and aspiration port 1840are contemplated under the invention, as is described in enabling detailhereinbelow. Each of ablation electrode 1810 and digestion electrode1820 may be constructed from a material comprising a metal such astungsten, stainless steel alloys, platinum or its alloys, titanium orits alloys, molybdenum or its alloys, nickel or its alloys, aluminum,gold, or copper, and the like. One material for construction of ablationelectrode 1810 and digestion electrode 1820 is platinum, or various ofits alloys.

[0319]FIG. 51A shows a longitudinal section of shaft distal end 1802 aof probe 1800, according to another embodiment of the invention, whereinablation electrode 1810 is mounted on shaft distal terminus 1806. Shaftdistal end 1402 a includes port 1440 leading to aspiration lumen 1442.In this embodiment, digestion electrode 1820 is mounted proximal toablation electrode 1810 within lumen 1442. Digestion electrode 1820 isshown in FIG. 51A as being mounted in the distal region of lumen 1442adjacent to port 1440, however, according to certain embodiments of theinvention, ablation electrode 1810 may be located within lumen 1442 moredistant from port 1440. In this configuration, ablation electrode 1810may be readily brought into contact with tissue at a site targeted fortreatment, while digestion electrode 1820 does not contact the tissue atthe target site and electrode 1820 remains remote from the target site.

[0320] Ablation electrode 1810 and digestion electrode 1820 haveablation electrode lead 1811 and digestion electrode lead 1821,respectively. Ablation electrode lead 1811 and digestion electrode lead1821 may be coupled to connection block 1805, substantially as describedwith reference to FIG. 50A. FIG. 51B shows an end view of distalterminus 1806 of electrosurgical probe 1800, taken along the lines51B-51B of FIG. 51A. Ablation electrode 1810 and digestion electrode1820 are each represented as a rectangular box, wherein digestionelectrode 1820 is located at approximately six o'clock within aspirationlumen 1842. However, various other shapes, locations, etc. forelectrodes 1810, 1820 are possible under the invention. A plurality offluid delivery ports 1830 are also located on shaft distal terminus 1806adjacent to ablation electrode 1810. Ports 1830 serve to deliverelectrically conductive fluid to tissue at a target site, or to ablationelectrode 1810 before or during a surgical procedure, e.g., as describedhereinabove with reference to FIGS. 34A, 44A-D. Although two ports 1830are shown in FIG. 51B as being substantially ovoid, other shapes,arrangements, and numbers of ports 1830 are also within the scope of theinvention.

[0321]FIG. 52A is a longitudinal section of a probe 1800, according toanother embodiment of the invention, in which ablation electrode 1810and digestion 1820 are mounted on an electrode support 1808 at shaftdistal terminus 1806. Ablation and digestion electrode leads 1811, 1821are omitted for the sake of clarity. FIG. 52B is an end view of shaftdistal terminus 1806, taken along the lines 52B-52B of FIG. 52A. Support1808 includes a central bore or void 1840′ (FIGS. 53B-D), wherein bore1840′ defines an opening to aspiration port 1840/lumen 1842. Ablationelectrode 1810 and digestion electrode 1820 are shown in FIG. 52A asbeing in the same plane or substantially the same plane. However,according to various alternative embodiments of the invention, ablationand digestion electrodes 1810, 1820 may be in different planes.Typically, ablation and digestion electrodes 1810, 1820 are in the sameplane, or digestion electrode 1820 is located proximal to ablationelectrode 1810 In the former situation, (i.e., ablation and digestionelectrodes 1810, 1820 are in the same plane) by advancing probe 1800towards the target site at a suitable angle, ablation electrode 1810 maycontact the tissue at the target site while digestion electrode 1820avoids contact with the tissue. In the latter situation (i.e., digestionelectrode 1820 is located proximal to ablation electrode 1810 (e.g.,FIGS. 51A, 57A)), probe 1800 is configured such that digestion electrode1820 easily avoids contact with tissue at a site targeted for resectionby ablation electrode 1810, regardless of the angle at which probe 1800approaches the tissue.

[0322] The structure of an electrode support 1808 according to oneembodiment is perhaps best seen in FIGS. 53A-D. FIG. 53A shows support1808, unmounted on shaft 1802, as seen from the side. FIG. 53B is aperspective view of support 1808, including bore 1840′ and afrusto-conical distal surface 1809. FIG. 53C is a face or end view ofsupport 1808 showing bore 1840′, and frusto-conical distal surface 1809.Support 1808 may include one or more mounting holes 1807 adapted formounting support 1808 to shaft 1802, or for mounting ablation anddigestion electrodes 1810, 1820 to support 1808. Mounting holes 1807 mayalso be used for passing electrode leads 1811, 1821, therethrough.Although four mounting holes 1807 are shown substantially equidistantfrom each other in FIG. 53C, other numbers and arrangements of mountingholes 1807 are possible under the invention. In some embodiments,mounting holes 1807 are strategically located on support 1808, forexample, to specifically accommodate the precise size, number, andarrangement of electrodes to be mounted or affixed thereto. FIG. 53D isa sectional view of support 1808 taken along the lines 53D-53D of FIG.53C illustrating the geometry of support 1808 including surface 1809. Insome embodiments, ablation electrode 1810 may be mounted on surface1809. In certain embodiments, both ablation electrode 1810 and digestionelectrode 1820 may be mounted on surface 1809. Support 1808 may comprisea rigid or substantially rigid, durable or refractory insulatingmaterial. In one embodiment, support 1808 comprises a material such as aceramic, a glass, a silicone rubber, or the like.

[0323]FIG. 54 shows a sectional view of electrode support 1808 of anelectrosurgical probe 1800, in which a portion of frusto-conical surface1809 (see, e.g., FIG. 53B) has been removed to provide a narrowerfrusto-conical surface 1809 a and a recessed surface 1809′. In thisembodiment, ablation electrode 1810 may be mounted on a distal portionof surface 1809 for making facile contact with tissue to be treated orremoved. Such an arrangement for ablation electrode 1810 promotes rapidand aggressive tissue removal from a target site. Digestion electrode1820, in contrast, may be disposed on recessed surface 1809′ to avoiddirect contact of electrode 1820 with tissue. As described hereinabove,the presence of tissue in the vicinity of digestion electrode 1820 maytrigger the switching of electric power from ablation electrode 1810 todigestion electrode 1820. By avoiding direct contact of electrode 1820with tissue at a site targeted for treatment, digestion electrode 1820is prevented from preferentially receiving electric power from the powersupply over an extended time period. This situation is undesirable inthat when the digestion electrode 1820 preferentially receives electricpower (i.e., functions as active electrode), there is concomitanttransfer of electric power away from ablation electrode 1810. Underthese circumstances, ablation electrode 1810 functions as returnelectrode, and consequently tissue at the target site is not efficientlyremoved via the cool ablation mechanism of the invention.

[0324]FIG. 55 shows a sectional view of electrode support 1808 of anelectrosurgical probe 1800 in which a groove 1814 is formed infrusto-conical surface 1809 (see, e.g., FIG. 53B) to provide an outersurface 1809 a and an inner surface 1809 b. In this embodiment, ablationelectrode 1810 may be mounted on outer surface 1809 a for making facilecontact with tissue and efficient tissue removal, essentially asdescribed with reference to FIG. 54. In the embodiment of FIG. 55,however, digestion electrode 1820 is disposed within groove 1814. Inthis manner, electrode 1820 avoids routine contact with tissue, andprobe 1800 of FIG. 55 enjoys the advantages expounded with respect tothe embodiment of FIG. 54, namely the futile reversal of role ofelectrodes 1810, 1820 triggered by tissue in the presence of electrode1820.

[0325]FIG. 56A shows, in longitudinal section, a shaft distal end 1802 aof an electrosurgical probe 1800, according to another embodiment of theinvention, wherein digestion electrode 1820 is disposed on support 1808and extends across aspiration port 1840/bore 1840′. In one embodiment,digestion electrode 1820 has a first end attached to electrode lead 1821(e.g., FIGS. 57A, 57B), and a second free end. In another embodiment,digestion electrode 1820 is in the form of a flat wire or metal ribbon(e.g., FIG. 58). Ablation electrode 1810 is located on surface 1809 ofsupport 1808 distal to digestion electrode 1820. FIG. 56B shows thedistal end of probe 1800, taken along the lines 56B-56B of FIG. 56A,illustrating a plurality of attachment units 1822 for affixing electrode1810 to support 1808. In this embodiment, support 1808 occupies themajority of shaft distal terminus 1806. Ablation electrode 1810 ismounted on support 1808, has a substantially semi-circular shape, andpartially surrounds aspiration port 1840. FIG. 56C is a side view ofshaft distal end 1802 a showing attachment of ablation electrode 1810 toelectrode support 1808, according to one embodiment of the invention.Although FIG. 56C shows ablation electrode 1810 affixed to electrodesupport 1808 via ball wires, other attachment methods are also withinthe scope of the invention. Methods for attachment of electricallyconductive solids (e.g., metals) to insulating solid supports are wellknown in the art. Ablation electrode 1810 is coupled to connection block1805 via electrode lead 1811. Lead 1811 may pass through mounting hole1807.

[0326]FIG. 57A shows a longitudinal section of shaft distal end 1802 aof a probe 1800, according to another embodiment of the invention. Inthis embodiment, digestion electrode 1820 is arranged within aspirationlumen 1842. Ablation electrode 1810 is located distal to aspiration port1840 and is coupled to lead 1811. FIG. 57B shows, in end view, thedistal end portion 1802 a of probe 1800, taken along the lines 57B-57Bof FIG. 57A. Digestion electrode 1820 of FIGS. 57A, 57B is in the formof a flat wire or metal ribbon. Electrode 1820 has a first end 1820 aand a second free end 1820 b. First end 1820 a is connected to lead 1821(FIG. 57A). In contrast, in this embodiment, free end 1820 b terminateswithout contacting an electrically conductive material, for example freeend 1820 b terminates in a wall of aspiration lumen 1842, wherein lumen1842 comprises an electrically insulating material. As an example, lumen1842 may comprise a plastic tube or cylinder having electricallyinsulating properties. By arranging for free end 1820 b to dead-end orterminate without contacting an electrically conductive material,Applicants have found improved generation and maintenance of a plasma inthe vicinity of electrode 1820 upon application of a suitable highfrequency voltage thereto. As is described fully hereinabove, thepresence of a plasma is a key factor in efficient ablation of tissuesvia the cool ablation (Coblation®) mechanism of the invention. Withoutintending to be bound in any way by theory, Applicants believe that byarranging for free end 1820 b to terminate without contacting anelectrically conductive material, when electric power is preferentiallysupplied to electrode 1820, distribution of power along the length ofelectrode 1820 is asymmetric and is highly concentrated at certainlocations. In this way, localized high current densities are produced inthe vicinity of some region(s) of electrode 1820, thereby promotingplasma formation.

[0327]FIG. 58 is a perspective view of a digestion electrode 1820,according to one embodiment of the invention. Although electrode 1820 isshown as having an arch shape, other shapes including planar or flat,circular or rounded, helical, etc., are also within the scope of theinvention. Similarly, although electrode 1820 is shown as a flat wire orribbon, i.e., as having a substantially rectangular cross-sectionalshape, many other cross-sectional shapes for electrode 1820 are alsopossible under the invention. As an example, electrode 1820 may have oneor more of the cross-sectional shapes described hereinabove, forexample, with reference to FIGS. 39A-I.

[0328]FIG. 59A shows, in longitudinal section, shaft distal end 1802 aof an electrosurgical probe 1800, wherein ablation electrode 1810 ismounted laterally on shaft 1802. In this embodiment, shaft distalterminus 1806 may have a rounded shape. Ablation electrode 1810 iscoupled to lead 1811 for connecting electrode 1810 to connection block1805. Digestion electrode 1820 is disposed proximal to ablationelectrode 1810 within aspiration lumen 1842. FIG. 59B shows shaft distalend 1802 a of FIG. 59A in plan view. Ablation electrode 1810 may bemounted on an electrode support (e.g., FIGS. 60A-B). Ablation electrode1810 and digestion electrode 1820 are each represented in FIGS. 52A-B asa rectangular box. However, various other shapes, locations, etc. forelectrodes 1810, 1820 are possible under the invention.

[0329]FIG. 60A shows a plan view of shaft distal end 1802 a of anelectrosurgical probe 1800, having ablation and digestion electrodes1810, 1820 mounted laterally on shaft distal end 1802 a, according toanother embodiment of the invention. Ablation electrode 1810 partiallyencircles aspiration port 1840, and is mounted on electrode support1808. Electrode support 1808 may be a hard or durable electricallyinsulating material of the type described hereinabove. A pair ofdigestion electrodes 1820 are disposed proximal to ablation electrode1810 and extend across port 1840. FIG. 60B shows a transversecross-section of shaft distal end 1802 a taken along the lines 60B-60Bof FIG. 60A. Ablation electrode 1810 may be in the form of a metalscreen, a metal plate, a wire, or a metal ribbon. In one embodiment,ablation electrode 1810 may comprise a semicircular screen or platecomprising platinum or one of its alloys. Digestion electrode 1820 maybe a wire or metal ribbon which may be straight, twisted, looped invarious directions, or helical. In one embodiment, digestion electrode1820 is a ribbon or flattened wire comprising platinum or one of itsalloys. Other compositions, numbers, shapes and arrangements of ablationelectrode 1810 and digestion electrode 1820 are also within the scope ofthe invention. A fluid delivery port 1830 is located proximal toablation electrode 1810. Port 1830 serves to deliver electricallyconductive fluid to tissue at a target site or to ablation electrode1810 before or during a surgical procedure. Although port 1830 is shownin FIG. 60A as being substantially crescent shaped, other shapes,arrangements, and numbers of port 1830 are also within the scope of theinvention.

[0330]FIG. 61 schematically represents a series of steps involved in amethod of removing tissue from a target site to be treated using anelectrosurgical system, according to another embodiment of theinvention, wherein step 1900 involves coupling an electrosurgical probeto a power supply unit. The probe may be a probe having the elements,structures, features or characteristics described herein, e.g., withreference to FIG. 49 through FIG. 60B. In particular the probe, has twotypes of electrodes, one or more ablation electrodes and one or moredigestion electrodes. The two types of electrodes are independentlycoupled to opposite poles of the power supply so that current can flowtherebetween. In one embodiment, the ablation electrode(s) are adaptedfor aggressively removing tissue, including cartilage tissue, from aregion of tissue to be treated; and the ablation electrode(s) areadapted for breaking down tissue fragments, e.g. resected tissuefragments dislodged by the ablation electrode(s), into smaller fragmentsor low molecular weight ablation byproducts. Both the ablation anddigestion electrodes are adapted for performing tissue ablation in acool ablation process, i.e., a plasma is generated in the presence of anelectrically conductive fluid, and the plasma induces moleculardissociation of high molecular weight tissue components into lowmolecular weight by-products. During such a process, the tissue treatedor removed may be exposed to a temperature generally not exceeding 90°C., and typically in the range of from about 45° to 90° C., moretypically from about 55° to 75° C.

[0331] The power supply may be, for example, power supply 428 (FIG. 7).Preferably, the power supply to which the probe is coupled is capable ofproviding to the probe a high frequency (e.g., RF) voltage of a selectedvoltage level and frequency. The selected voltage frequency is typicallybetween about 5 kHz and 20 MHz, essentially as described hereinabove.The RMS voltage will usually be in the range of from about 5 volts to1000 volts, and the peak-to-peak voltage will be in the range of fromabout 10 to 2000 volts, again as described hereinabove. Step 1902involves positioning the probe adjacent to target tissue. For example,the probe distal end may be advanced towards target tissue such that theablation electrode is in the vicinity of the tissue at the site targetedfor treatment. By way of a more specific example, the ablation electrodemay be brought adjacent to the meniscus during arthroscopic surgery ofthe knee. In one aspect, the probe may be positioned with respect totarget tissue such that the ablation electrode is in contact with tissueat the target site, while the digestion electrode is not in contact withthe tissue at the target site. In one embodiment, the digestionelectrode may be located substantially proximal to the ablationelectrode, such that when the ablation electrode is in the presence ofthe tissue at the target site, the digestion electrode is somewhatdistant from the tissue at the target site. For example, the ablationelectrode may be positioned terminally on the shaft or near the terminusof the shaft, while the digestion electrode may be positioned within theaspiration lumen.

[0332] Step 1904 involves supplying power from the power supply to theablation electrode. Typically, when the ablation electrode is in thepresence of tissue, the power supply preferentially supplies power tothe ablation electrode, and under these circumstances the ablationelectrode generally serves as active electrode. (During a differentphase or step of the procedure, the ablation electrode may undergo areversal of roles to function as a return electrode (step 1912)).Supplying power of a suitable frequency and voltage to the ablationelectrode in the presence of an electrically conductive fluid causes aplasma to be generated in the vicinity of the ablation electrode. Theplasma generated leads to the localized removal of tissue via a coolablation mechanism (Coblation®), as described hereinabove. In oneembodiment, step 1904 involves preferentially supplying power from thepower supply to the ablation electrode, largely to the exclusion of thedigestion electrode. That is to say, at any given time point, power fromthe power supply is supplied preferentially to one or the other of thetwo types of electrodes, such that the ablation electrode (or thedigestion electrode, step 1912) may receive up to about 100% of thepower from the power supply. In this way, the power available from thepower supply is used efficiently by the electrode which receives thepower (i.e., the electrode functioning as the active electrode) for theaggressive generation of a plasma and ablation of tissue.

[0333] Optional step 1906 involves delivering an electrically conductivefluid, e.g., isotonic saline, a gel, etc., to the target site or to theablation electrode. In a wet field procedure, wherein an electricallyconductive fluid is already present, step 1906 may be omitted. Step 1906may be performed before, during, or after the performance of step 1904.Also, step 1906 may be repeated as often as is appropriate during thecourse of a surgical procedure. Step 1906 may be achieved by deliveringan electrically conductive fluid via a fluid delivery device which isintegral with the electrosurgical probe, or via an ancillary device.Step 1908 involves removing tissue from the target site with theablation electrode via a cool ablation mechanism of the invention. Step1908 leads to molecular dissociation of tissue components and results inthe formation of low molecular weight by-products. Depending on thenature of the tissue, the voltage level, and other parameters, step 1908may also result in the formation of resected tissue fragments. In oneembodiment, step 1908 involves aggressively removing tissue from thetarget site such that tissue fragments may be resected from the targetsite by the ablation electrode due, at least in part, to the generationof an aggressive plasma in the vicinity of the target site (step 1904).

[0334] Step 1910 involves aspirating materials from the target site.Materials thus aspirated may include electrically conductive body fluids(e.g., synovial fluid, blood), extrinsic electrically conductive fluids(e.g., isotonic saline supplied in step 1906), and resected tissuefragments. Such materials may be aspirated from the target site via anaspiration device integral with the electrosurgical probe, as describedhereinabove. The aspirated materials which pass from the target sitethrough the aspiration device constitute an aspiration stream.

[0335] Step 1912 involves supplying power to the digestion electrode. Inone embodiment, step 1912 involves supplying power to the digestionelectrode largely to the exclusion of the ablation electrode. That is tosay, during step 1912 up to about 100% of the power from the powersupply may be supplied to the digestion electrode. Under thesecircumstances, the digestion electrode serves as an active electrode,and the ablation electrode serves as a return electrode. Typically, thedigestion electrode preferentially receives power from the power supplyunder circumstances where the digestion electrode is in the presence oftissue, for example, one or more resected tissue fragments in theaspiration stream adjacent to the digestion electrode.

[0336] Step 1914 involves ablating any resected tissue fragments presentin the aspiration stream to form low molecular weight ablationby-products. Typically, the digestion electrode is arranged in relationto the aspiration device such that the aspiration stream contacts thedigestion electrode. For example, the digestion electrode may beadjacent to or proximal to an aspiration port, or the digestionelectrode may be located within an aspiration lumen. Typically, ablationof resected tissue fragments is accomplished by the digestion electrodein a cool ablation process, as described hereinabove. In one embodiment,the electrosurgical system may be triggered to “switch” power from theablation electrode to the digestion electrode by changes in electricalimpedance in the aspiration stream in the vicinity of the digestionelectrode. Such localized changes in impedance may result from theproximity of resected tissue fragments to the digestion electrode.Triggering a switch in the power away from the ablation electrode and tothe digestion electrode may be dependent on the surface area ratio ofthe ablation and digestion electrodes. In one aspect of the invention,steps 1912, 1914 represent a transient, intermittent phase of operationof the electrosurgical system/probe. For example, immediately after thecompletion of step 1914, the ablation electrode may resume its role asactive electrode, and concomitantly therewith the digestion electrodemay revert to its role as return electrode. For instance, in the absenceof resected tissue fragments in the vicinity of the digestion electrode,the power may be switched away from the digestion electrode and insteadthe power may be supplied preferentially to the ablation electrode. Inthis way, once power to the probe has been turned on by the operator(surgeon), steps 1904 and 1908 through 1912 may be repeated numeroustimes in rapid succession during the course of a surgical procedure,without operator intervention or input. As already noted above, step1906 may also be repeated as appropriate.

[0337]FIGS. 62A and 62B show a side view and an end-view, respectively,of an electrosurgical suction apparatus 2100, according to anotherembodiment of the invention. Apparatus 2100 generally includes a shaft2102 having a shaft distal end portion 2102 a and a shaft proximal endportion 2102 b, the latter affixed to a handle 2104. An aspiration tube2144, adapted for coupling apparatus 2100 to a vacuum source, is joinedat handle 2104. An electrically insulating electrode support 2108 isdisposed on shaft distal end portion 2102 a. Electrode support 2108 maycomprise a durable or refractory material such as a ceramic, a glass, afluoropolymer, or a silicone rubber. In one embodiment, electrodesupport 2108 comprises an alumina ceramic. A plurality of activeelectrodes 2110 are arranged on electrode support 2108.

[0338] Shaft 2102 may comprise an electrically conducting material, suchas stainless steel alloys, tungsten, platinum or its alloys, titanium orits alloys, molybdenum or its alloys, and nickel or its alloys. Aninsulating sleeve 2118 covers a portion of shaft 2102. An exposedportion of shaft 2102 located between sleeve distal end 2118 a andelectrode support 2108 defines a return electrode 2116. In analternative embodiment (not shown), shaft 2102 may comprise aninsulating material and a return electrode may be provided on the shaft,for example, in the form of an annulus of an electrically conductivematerial.

[0339]FIG. 62B shows an end-view of apparatus 2100, taken along thelines 62B-62B of FIG. 62A. A plurality of active electrodes 2110 arearranged substantially parallel to each other on electrode support 2108.A void within electrode support 2108 defines an aspiration port 2140.Typically, the plurality of active electrodes 2110 span or traverseaspiration port 2140, wherein the latter is substantially centrallylocated within electrode support 2108. Aspiration port 2140 is incommunication with an aspiration channel 2142 (FIG. 62C) for aspiratingunwanted materials from a surgical site.

[0340]FIG. 62C shows a longitudinal cross-section of the apparatus ofFIG. 62A. Aspiration channel 2142 is in communication at its proximalend with aspiration tube 2144. Aspiration port 2140, aspiration channel2142, and aspiration tube 2144 provide a convenient aspiration unit orelement for removing unwanted materials, e.g., ablation byproducts,excess saline, from the surgical field during a procedure. The directionof flow of an aspiration stream during use of apparatus 2100 isindicated by the solid arrows. Handle 2104 houses a connection block2105 adapted for independently coupling active electrodes 2110 andreturn electrode 2116 to a high frequency power supply (e.g., FIG. 1).An active electrode lead 2121 couples each active electrode 2110 toconnection block 2105. Return electrode 2116 is independently coupled toconnection block 2105 via a return electrode connector (not shown).Connection block 2105 thus provides a convenient mechanism forindependently coupling active electrodes 2110 and return electrode 2116to a power supply (e.g., power supply 28, FIG. 1).

[0341]FIG. 63A is a longitudinal cross-section of the shaft distal end2102 a of an electrosurgical suction apparatus 2100, showing thearrangement of active electrode 2110 according to one embodiment. Activeelectrode 2110 includes a loop portion 2113, a free end 2114, and aconnected end 2115. Active electrode 2110 is disposed on electrodesupport 2108, and is in communication at connected end 2115 with activeelectrode lead 2121 for coupling active electrode 2110 to connectionblock 2105. Aspiration channel 2142 is omitted from FIG. 63A for thesake of clarity. FIG. 63B is a cross-section of active electrode 2110 astaken along the lines 63B-63B of FIG. 63A, showing an electrode distalface 2111. Although FIG. 63B shows a substantially rectangular shape foractive electrode 2110, other shapes (e.g., those depicted in FIGS.39A-I) are also possible under the invention.

[0342]FIG. 63C shows in more detail active electrode 2110 in the form ofa loop of flattened wire in communication with electrode lead 2121,according to one embodiment of the invention. Typically, free end 2114terminates within electrode support 2108 or within another electricallyinsulating material. In this embodiment, electrode lead 2121 is integralwith active electrode 2110. Electrode lead 2121 and active electrode2110 may each comprise a highly conductive, corrosion-resistant metalsuch as tungsten, stainless steel alloys, platinum or its alloys,titanium or its alloys, molybdenum or its alloys, nickel or its alloys,iridium, aluminum, gold, copper, and the like. In one embodiment, one orboth of electrode lead 2121 and active electrode 2110 may each comprisea platinum/iridium alloy, such as an alloy comprising from about 85% to95% platinum and from about 5% to 15% iridium.

[0343]FIG. 64A shows an electrosurgical suction apparatus 2100 having anouter sheath 2152 external to shaft 2102 to provide an annular fluiddelivery channel 2150, according to another aspect of the invention. Thedistal terminus of outer sheath 2152 defines an annular fluid deliveryport 2156 at a location proximal to return electrode 2116. Outer sheath2152 is in communication at its proximal end with a fluid delivery tube2154 at handle 2104. Fluid delivery port 2156, fluid delivery channel2150, and tube 2154 provide a convenient fluid delivery unit forproviding an electrically conductive fluid (e.g., isotonic saline) tothe distal end of the suction apparatus or to a target site undergoingtreatment. The direction of flow of an electrically conductive fluidduring use of apparatus 2100 is indicated by the solid arrows. Anextraneous electrically conductive fluid forms a current flow pathbetween active electrodes 2110 and return electrode 2116, and canfacilitate generation of a plasma in the vicinity of active electrodes2110, as described hereinabove. Provision of an extraneous electricallyconductive fluid may be particularly valuable in a dry field situation(e.g., in situations where there is a paucity of native electricallyconductive bodily fluids, such as blood, synovial fluid, etc.). In analternative embodiment, an electrically conductive fluid, such assaline, may be delivered to the distal end of suction apparatus 2100 bya separate device (not shown). FIG. 64B is a transverse cross-section ofshaft 2102 of the apparatus of FIG. 64A, and shows the relationshipbetween outer sheath 2152, shaft 2102, and fluid delivery port 2156.Aspiration channel 2142 and electrode lead 2121 are omitted from FIGS.64A, 64B for the sake of clarity.

[0344] With reference to FIG. 65A there is shown in longitudinalcross-section the shaft distal end 2102 a of an electrosurgical suctionapparatus 2100 including a baffle or trap 2146, according to anotherembodiment, wherein baffle 2146 is arranged transversely within shaft2102 at the distal end of aspiration channel 2142. In the embodimentshown, baffle 2146 is recessed with respect to treatment surface 2109 todefine a holding chamber 2148 within the void of electrode support 2108.As seen in the end view of FIG. 65B, baffle 2146 includes a plurality ofaspiration ports 2140′. A plurality of active electrodes 2110 arearranged substantially parallel to each other on electrode support 2108.During a procedure involving resection or ablation of tissue, anyrelatively large resected tissue fragments or other tissue debris drawnby suction to a location proximal to active electrodes 2110 may beretained by baffle 2146 within holding chamber 2148. By relatively largeresected tissue fragments is meant those fragments too large to bereadily drawn through ports 2140′ in an aspiration stream. Such tissuefragments temporarily retained by baffle 2146 are convenientlypositioned with respect to active electrodes 2110, and are readilydigested by one or more of active electrodes 2110 by a suitable highfrequency voltage applied between active electrodes 2110 and returnelectrode 2116. As an additional advantage, because aspiration channel2142 is wider than each of aspiration ports 2140′, the former is notsubject to being clogged by resected tissue fragments or other debris.Using the configuration of FIGS. 65A, 65B only aspirations ports 2140′are subject to (temporary) blockage; as pointed out above, any tissuefragments too large to pass through ports 2140′ are rapidly digested byactive electrodes 2110. Baffle 2146 may be constructed from anelectrically insulating material, such as various plastics.Alternatively, baffle 2146 may comprise an electrically conductingmaterial such as various metals, in which case baffle 2146 is typicallyelectrically isolated.

[0345]FIG. 66A is a longitudinal cross-section of a shaft distal end2102 a of a suction apparatus 2100, according to another embodiment,wherein shaft distal end 2102 a is curved. The distal end of electrodesupport 2108 defines a treatment surface 2109 (the latter perhaps bestseen in FIG. 67A). A curve in shaft distal end 2102 a may facilitateaccess of treatment surface 2109 to a site targeted for electrosurgicaltreatment. Active electrodes 2110, which typically protrude fromtreatment surface 2109 (e.g., FIGS. 67A, 67B), are omitted from FIG. 66Afor the sake of clarity.

[0346]FIG. 66B is a longitudinal cross-section of shaft distal end 2102a of a suction apparatus 2100, according to another embodiment of theinvention, wherein the distal end of electrode support 2108 is beveledat an angle, . . . . Typically angle is in the range of from about 15°to 60°, more typically from about 20° to 45°, and usually from about 25°to 35°. Active electrodes 2110 are omitted from FIG. 66B for the sake ofclarity. A beveled treatment surface 2109 may facilitate access of shaftdistal end portion 2102 a to tissue at a target site as well asmanipulation of shaft 2102 during treatment.

[0347]FIG. 67A shows a specific configuration of a shaft distal end 2102a of an electrosurgical suction apparatus 2100, according to oneembodiment of the invention. The distal end of electrode support 2108defines a beveled treatment surface 2109. A first, a second, and a thirdactive electrode 2110 a,b,c extend from treatment surface 2109.Treatment surface 2109 includes a rounded perimeter 2107 which serves toeliminate sharp edges from electrode support 2108. The presence ofrounded perimeter 2107 prevents mechanical damage to delicate orsensitive tissues during use of apparatus 2100. Electrode support 2108encircles aspiration port 2140.

[0348] Loop portions 2113 (e.g., FIG. 63C) of first, second, and thirdactive electrodes, 2110 a, 2110 b, 2110 c, traverse or bridge aspirationport 2140. First, second, and third active electrodes, 210 a, 2110 b,2110 c are arranged substantially parallel to each other, and protrudefrom treatment surface 2109. In the case of second active electrode 2110b, the orientation with respect to treatment surface 2109 of free end2114, loop portion 2113, and connected end 2115 is at leastsubstantially the same. In contrast, in the case of first and thirdactive electrodes 2110 a, 2110 c, the orientation with respect totreatment surface 2109 of loop portion 2113 is different from theorientation of connected end 2115 and free end 2114. That is to say, theorientation of active electrodes 2110 a and 2110 c with respect totreatment surface 2109 changes from a first direction in the region ofconnected end 2115 and free end 2114, to a second direction in theregion of loop portion 2113.

[0349] Furthermore, loop portions 2113 of first, second, and thirdactive electrodes, 2110 a, 2110 b, 2110 c are oriented in differentdirections. Thus, second electrode 2110 b extends substantially in thedirection of the longitudinal axis of shaft 2102, and distal face 2111 bis also oriented in the direction of the longitudinal axis of shaft2102. First and third electrodes 2110 a, 2110 c flank second electrode2110 b, loop portions 2113 of first and second electrodes 2110 a, 2110 care oriented towards second electrode 2110 b, and distal faces 2111 a,2111 c both face towards second electrode 2110 b. In other words, first,second, and third electrodes 2110 a, 2110 b, 2110 c all point indifferent directions.

[0350] Perhaps as best seen in FIG. 67B, each active electrode 2110 a-cincludes a distal face 2111 a-c. In the embodiment of FIGS. 67A, 67B,each distal face 2111 a, 2111 b, 211 Ic faces, or is oriented in, adifferent direction as described with reference to FIG. 67A.Furthermore, a dashed line L_(p) drawn parallel to treatment surface2109 illustrates that the orthogonal distance, D_(o) from treatmentsurface 2109 to each distal face 2111 a,b,c is substantially the samefor each of active electrodes 2110 a,b,c.

[0351] Electrosurgical suction apparatus 2100 described with referenceto FIGS. 62A through 67B can be used for the removal, resection,ablation, and contouring of tissue during a broad range of procedures,including procedures described hereinabove with reference to otherapparatus and systems of the invention. Typically during suchprocedures, the apparatus is advanced towards the target tissue suchthat treatment surface 2109 and active electrodes 2110 are positioned soas to contact, or be in close proximity to, the target tissue. Each ofthe plurality of active electrodes includes a loop portion adapted forablating tissue via molecular dissociation of tissue components uponapplication of a high frequency voltage to the apparatus. In oneembodiment, an electrically conductive fluid may be delivered to thedistal end of the apparatus via a fluid delivery channel to provide aconvenient current flow path between the active and return electrodes. Ahigh frequency voltage is applied to the apparatus from a high frequencypower supply to ablate the tissue at the target site. Suitable valuesfor various voltage parameters are presented hereinabove.

[0352] Unwanted materials, such as low molecular weight ablationby-products, excess extraneously supplied fluid, resected tissuefragments, blood, etc., are conveniently removed from the target sitevia the integral aspiration unit of the invention. Typically, such anaspiration unit comprises an aspiration channel in communication with adistal aspiration port and a proximal aspiration tube, the lattercoupled to a suitable vacuum source (not shown). Vacuum sources suitablefor use in conjunction with apparatus and systems of the invention arewell known in the art.

[0353] In one embodiment, the apparatus may be reciprocated or otherwisemanipulated during application of the high frequency voltage, such thatloop portion 2113 including distal face 2111 of each active electrodemoves with respect to the target tissue, and the tissue in the region ofeach distal face 2111 is ablated via molecular dissociation of tissuecomponents. The apparatus is capable of effectively removing tissue in ahighly controlled manner, and is particularly useful in proceduresrequiring a smooth and/or contoured tissue surface.

[0354]FIG. 68A is a block diagram representing an electrosurgical system2200, according to another embodiment of the invention. System 2200generally includes an electrosurgical probe 2201 coupled to a highfrequency power supply 2203. FIG. 68B is a block diagram representingelectrosurgical probe 2201, including a working portion 2206, a shaft2202, and a handle 2204. Working portion 2206 includes an electrodeassembly 2210 having a plurality of active electrodes (e.g., FIG. 71A).Typically, handle 2204 houses a connection block 2205 by which each ofthe plurality of active electrodes of electrode assembly 2210 may beconveniently coupled to high frequency power supply 2203. Probe 2201further includes an aspiration unit 2230, having a plurality ofaspiration ports 2240 in communication with an aspiration channel 2242.Typically, channel 2242 is coupled to a suitable vacuum source (notshown) via an aspiration tube 2244. Each of the plurality of aspirationports 2240 is adapted for aspirating materials, e.g., fluids, from thevicinity of working portion 2206 during a surgical procedure.

[0355] FIGS. 69A-69C each schematically represent a working portion ofan electrosurgical probe 2201, according to the instant invention. Eachworking portion (2206, 2206′, 2206″) includes a plurality of workingzones (e.g., 2208 a-n, FIG. 69A). Each working zone typically includesat least one active electrode and at least one aspiration port. Ingeneral, the suction pressure in a given working zone is proportional tothe aspiration rate via the aspiration ports of that zone. For asituation in which each of the plurality of aspiration ports is coupledto a common aspiration channel 2242, the suction pressure of eachworking zone is a function of the number and size of the least oneaspiration port in that zone. Each active electrode is adapted forgenerating a plasma, when in the presence of an electrically conductivefluid and upon application of a high frequency voltage between theactive electrode and a return electrode. However, the extent to whichthe active electrode(s) in each zone form a plasma is dependent, inpart, on the local environment of that zone, wherein the localenvironment is determined by the aspiration rate. Thus, according to oneaspect of the invention, the propensity for each working zone toinitiate and maintain a plasma is a function of the suction pressure inthat zone.

[0356] While not being bound by theory, applicant has determined that arelatively low suction pressure (low aspiration rate) in a given zone isconducive to the facile initiation and maintenance of a plasma thereat,upon application of the high frequency voltage to the activeelectrode(s) disposed on that working zone. Thus, a relatively lowaspiration rate in a given working zone strongly promotes generation ofa plasma at that zone. Conversely, a relatively high suction pressure(high aspiration rate) in a particular zone generally results inrelatively weak generation of a plasma thereat. For electrosurgicalablation according to the invention, facile generation of a plasma at aworking zone generally results in rapid ablation of tissue; whereas weakgeneration of a plasma generally results in a relatively slow ablationrate. That is to say, the ablation rate of a working zone is determined,inter alia, by the aspiration rate of that zone. Therefore, by theappropriate selection of the number and/or size of aspiration port(s) ofthe various working zones of probe 2201, the relative rate of ablationof each working zone of probe 2201 can be controlled. According to oneaspect of the invention, during operation of probe 2201, a suctionpressure gradient may exist between each working zone of working portion2206.

[0357]FIG. 69A schematically represents a working portion 2206 of anelectrosurgical probe, according to one embodiment of the invention. Asshown, working portion 2206 includes a plurality of working zonesrepresented as zones 2208 a-n. Typically, each working zone, e.g., zone2208 a, of working portion 2206 may be differentiated from other workingzones, e.g., zone 2208 b and zone 2208 n, on the basis of its suctionpressure. That is to say, during operation of probe 2201, each workingzone 2208 a-n typically has a different suction pressure associatedtherewith. Consequently, each working zone 2208 a-n differs in itspropensity to form a plasma thereat, and is characterized by a differentablation rate. The plurality of working zones 2208 a-n may be located onthe same plane, or on different planes of working portion 2206 (e.g.,FIGS. 69B, 69C).

[0358]FIG. 69B schematically represents a working portion 2206′ of anelectrosurgical probe, according to another embodiment of the invention.As shown, working portion 2206′ includes a plurality of planes, viz.plane A 2207 a and plane B 2207 b, and a plurality of working zones2208′a and 2208′b, wherein each working zone 2208′a, 2208′b is locatedon a different plane of working portion 2206′. Each of working zones2208′a and 2208′b typically includes at least one aspiration port and atleast one active electrode. Typically, working zone 2208′a isdistinguishable from working zone 2208′b on the basis of its suctionpressure. That is to say, during operation of a probe 2201, workingzones 2208′a, 2208′b show different propensities to initiate andmaintain a plasma thereat. Accordingly, during operation of probe 2201,working zones 2208′a, 2208′b typically have dissimilar rates of ablationand dissimilar aspiration rates. By careful selection of the numberand/or size of aspiration ports of each of working zone 2208′a, 2208′b,the relative rate of ablation of working zones 2208′a and 2208′b can becontrolled.

[0359]FIG. 69C schematically represents working portion 2206″ of anelectrosurgical probe, according to another embodiment of the invention.As shown, a single plane, plane A′ 2207′a, includes a plurality ofworking zones 2208″a, 2208″b, and 2208″c. As described hereinabove, eachworking zone 2208″a, 2208″b, and 2208″c typically includes at least oneaspiration port and at least one active electrode. Typically, eachworking zone, e.g., zone 2208″a, is distinguishable from other workingzones, e.g., zones 2208″b, 2208″c, on the basis of its suction pressure.Because of the relationship between suction pressure of a given workingzone and its ablation rate, as described hereinabove, working zones2208″a, 2208″b, and 2208″c may each have a markedly different rate ofablation.

[0360]FIG. 70A is a longitudinal sectional view of an electrosurgicalprobe 2201, according to one embodiment of the invention. Probe 2201generally includes a shaft 2202 having a shaft distal end 2202 a and ashaft proximal end 2202 b, a working portion 2206 disposed on shaftdistal end 2202 a, and a handle 2204 affixed to shaft proximal end 2202b. Working portion 2206 comprises a first working zone 2208 a, and asecond working zone 2208 b. First working zone 2208 a lies on a firstplane 2207 a (FIG. 70B), which is beveled at an acute angle □ withrespect to the longitudinal axis of probe 2201. Angle □ is typically inthe range of from about 15° to 75°. Typically, each of first workingzone 2208 a and second working zone 2208 b includes at least one activeelectrode. (Active electrodes are omitted from FIG. 70A for the sake ofclarity.) Probe 2201 may further include a return electrode 2214. Handle2204 may include a connection block 2205 for conveniently coupling probe2201 to high frequency power supply 2203 (FIG. 68A). Typically, workingportion 2206 comprises an electrically insulating support 2220 (e.g.,FIG. 71A). Probe 2201 further includes an aspiration unit, whichcomprises an aspiration channel 2242 in communication at its distal endwith a plurality of aspiration ports 2240, 2240′ (FIG. 70B). Aspirationchannel 2242 is coupled at its proximal end to an aspiration tube 2244.Aspiration tube 2244 may be coupled to a suitable vacuum source (notshown) for aspirating fluids from first and second working zones 2208 a,2208 b via aspiration ports 2240, 2240′.

[0361] With reference to FIGS. 70A and 70B, the embodiment shownincludes a first set of aspiration ports 2240 arranged on first workingzone 2208 a, and a second set of aspiration ports 2240′ arranged onsecond working zone 2208 b. It can be seen, from an examination of FIGS.70A, 70B, that the combined area of aspiration ports 2240′ is greaterthan the combined area of aspiration ports 2240. Furthermore, aspirationports 2240′ on second working zone 2208 b are located proximal toaspiration ports 2240 on first working zone 2208 a. Because aspirationports 2240, 2240′ are in communication with a common aspiration channel2242, the aspiration rate from first working zone 2208 a is less thanthe aspiration rate from second working zone 2208 b. As a result, uponapplication of a high frequency voltage to active electrodes on workingportion 2206, first working zone 2208 a has a greater ability toinitiate and maintain an aggressive plasma as compared with secondworking zone 2208 b. By “aggressive plasma” is meant a plasma which iscapable of aggressively ablating target tissue. Consequently, firstworking zone 2208 a typically has a higher ablation rate as comparedwith second working zone 2208 b. Typically, ablation by each workingzone 2208 a, 2208 b is via plasma-induced molecular dissociation oftarget tissue components, as described hereinabove.

[0362] In one embodiment, the ablation rate of first working zone 2208 ais such that ablation of tissue results in production of resectedfragments of target tissue, as well as low molecular weight (or gaseous)ablation by-products. The low molecular weight ablation byproducts maybe removed from the surgical site by aspiration via aspiration ports2240 and/or 2240′, while the resected tissue fragments may be ablated orvaporized by second working zone 2208 b. Low molecular weight ablationby-products resulting from the ablation of the resected tissue fragmentsmay be aspirated via aspiration ports 2240′ of second working zone 2208b.

[0363] Probe 2201 may further include a fluid delivery unit (e.g., FIG.64A) for delivering an electrically conductive fluid to working portion2206, wherein the electrically conductive fluid provides a current flowpath between at least one active electrode and return electrode 2214.With reference to FIG. 70B, working zone 2208 a on first plane 2207 aincludes a plurality of fluid delivery ports 2256. Similarly, workingzone 2208 b on second plane 2207 b includes a plurality of fluiddelivery ports 2256′. Return electrode 2214, as well as a fluid deliverychannel (e.g., FIG. 64A), are omitted from FIG. 70B for the sake ofclarity.

[0364]FIG. 71A shows a perspective view of the distal portion of anelectrosurgical probe, according to another embodiment of the invention.An electrically insulating support 2220 is disposed on shaft distal end2202 a. Return electrode 2214 is located proximal to support 2220. Shaft2202 may comprise an electrically conducting material (e.g., stainlesssteel or other metal) or an electrically insulating material (e.g., apolyimide or other plastic). In the former situation, return electrode2214 may comprise an exposed (i.e., non-insulated) portion of shaft2202, while support 2220 may comprise a material such as a siliconerubber, a ceramic, or a glass.

[0365] With reference to FIGS. 71A and 71B, the distal end of support2220 is beveled to provide a single plane 2207. In the embodiment ofFIGS. 71A and 71B, working portion 2206 essentially occupies singleplane 2207. As shown, plane 2207 includes first, second, and thirdworking zones 2208′a, 2208′b, and 2208′c, respectively. Plane 2207 has aplurality of active electrodes 2212 a-c, and a plurality of aspirationports 2240, 2240′, 2240″. First working zone 2208′a includes a distalactive electrode 2212 a and has a single aspiration port 2240. Secondworking zone 2208′b is located proximal to first working zone 2208′a,and includes an active electrode 2212 b. Second working zone 2208′b hastwo aspiration ports 2240′, wherein aspiration ports 2240′ are somewhatlarger than aspiration port 2240. Similarly, third working zone 2208′c,which is located proximal to second working zone 2208′b, includes anactive electrode 2212 c and has two aspiration ports 2240″.

[0366] Aspiration ports 2240″ are significantly larger than aspirationports 2240′, and substantially larger than aspiration port 2240. As aresult, the total aspiration port area, and the aspiration rate,progressively increase for working zones 2208′a, 2208′b, 2208′c. Thus,an aspiration gradient (or suction pressure gradient) exists on plane2207, in which the suction pressure diminishes in a distal direction.Because of the relationship between suction pressure of a given workingzone and its ablation rate, as described hereinabove, a gradient ofablation rate exists on plane 2207, in which the rate of ablationdiminishes in a proximal direction.

[0367] From an examination of FIGS. 71A and 71B, it is apparent thataspiration ports 2240 and 2240″ are arranged near the periphery ofworking portion 2206. Applicant has found that arrangement of aspirationports around the periphery of the working portion of a probe facilitatesremoval of ablation by-products, and in particular the removal ofgaseous by-products entrapped within a liquid, during a procedure. Ofcourse, other peripheral arrangements for aspiration ports, other thanthat depicted in FIGS. 71A, 71B, are also within the scope of theinvention.

[0368] Active electrodes 2112 a-c are represented in FIG. 71A as beinglinear and arranged substantially orthogonal to the longitudinal axis ofthe probe. However, numerous other configurations and orientations ofactive electrodes are possible under the invention. For example, theactive electrodes may have any of the configurations describedhereinabove, e.g., with reference to FIGS. 62A through 67B.

[0369]FIG. 72 is a perspective view of the distal portion of anelectrosurgical probe, according to another embodiment of the invention,including electrode support 2220′ disposed on shaft distal end 2202 a.Electrode support 2220′ accommodates a working portion 2206′. Workingportion 2206′ includes a first, a second, and a third plane 2207 a, 2207b, 2207 c, respectively. A first working zone 2208″a on first plane 2207a has first aspiration ports 2240. A second working zone 2208″b and athird working zone 2208″c jointly occupy second plane 2207 b. Secondworking zone 2208″b and third working zone 2208″c have second aspirationports 2240′ and third aspiration ports 2240″, respectively. A fourthworking zone 2208″d lies on third plane 2207 c, and has fourthaspiration ports 2240′″.

[0370] As shown, first, second, third, and fourth aspiration ports 2240,2240′, 2240″, and 2240′″, respectively, progressively increase in size.As a result, a suction pressure gradient exists axially within workingportion 2206′, from the lowest suction pressure of first working zone2208″a to the highest suction pressure at fourth working zone 2208″d.Because of the relationship between suction pressure of a given workingzone and its ablation rate, as described hereinabove, the suctionpressure gradient of working portion 2206′ translates to a gradient ofablation rate within working portion 2206′. Although the gradient ofsuction pressure and ablation rate in the embodiment of FIG. 72 isaxial, a gradient of both suction pressure and ablation rate in otherorientations or directions is also contemplated and is within the scopeof the invention. Active electrodes are omitted from FIG. 72 for thesake of clarity.

[0371] It should be understood that mechanisms for controlling therelative suction pressure of two or more working zones, other than thesize, number, and arrangement of the aspiration port(s), are alsopossible under the invention. For example, the aspiration port(s) ofeach working zone may be coupled to a separate aspiration channel, andthe flow rate within each aspiration channel may be independentlycontrolled via valves.

[0372]FIG. 73A shows a perspective view of the distal end of anelectrosurgical probe, according to another embodiment of the invention.An electrode support 2320 is disposed on shaft distal end 2302 a, andincludes a first distal plane 2307 a and a second proximal plane 2307 b.First plane 2307 a is beveled at an angle, typically in the range offrom about 15° to 75°, with respect to the longitudinal axis of shaft2302. A first working zone 2308 a lies on first plane 2307 a, while asecond working zone 2308 b lies on second plane 2307 b. First workingzone 2308 a and second working zone 2308 b comprise a working portion2306. First working zone 2308 a includes a single aspiration port 2340,while second working zone 2308 b includes two aspiration ports 2340′a,2340′b. As shown, return electrode 2314 is located proximal and inferiorto electrode support 2320. However, other configurations for a returnelectrode are also within the scope of the invention. Each working zone2308 a, 2308 b has one or more active electrodes arranged thereon (FIG.73B). Active electrodes are omitted from FIG. 73A for the sake ofclarity.

[0373]FIG. 73B shows the distal portion of the probe of FIG. 73A in planview. First working zone 2308 a includes an active electrode 2312 in theform of a loop. As shown, active electrode 2312 extends acrossaspiration port 2340. Second working zone 2308 b includes two activeelectrodes 2312′a and 2312′b, each in the form of a loop, which extendacross aspiration ports 2340′a and 2340′b, respectively. In thisconfiguration, active electrodes 2312′a, 2312′b are strategicallylocated with respect to aspiration ports 2340′a, 2340′b so as to preventblockage of ports 2340′a and 2340′b by resected tissue fragments.

[0374] Each of active electrodes 2312, 2312′a, 2312′b may comprise ametal, such as tungsten, stainless steel, platinum, titanium,molybdenum, palladium, iridium, nickel, aluminum, gold, or copper, andthe like, or their alloys. In one embodiment, one or more of activeelectrodes 2312, 2312′a, 2312′b may comprise a platinum/iridium alloy,for example, an alloy having from about 80% to 95% platinum and fromabout 5% to 20% iridium, by weight. Other numbers, arrangements,configurations, and compositions for the active electrodes are alsowithin the scope of the invention.

[0375]FIG. 74 schematically represents a series of steps involved in amethod of ablating tissue, according to another embodiment of theinvention. It should be understood that systems, apparatus, and methodsof the invention are not limited to a particular target tissue orsurgical procedure, but instead are generally applicable to ablation ofa wide variety of different tissues during a broad range of procedures.Regardless, of the particular procedure and target tissue, methods ofthe instant invention are generally concerned with plasma-inducedablation of tissue via the molecular dissociation of tissue componentsto form low molecular weight (e.g., gaseous) by-products.

[0376] Again with reference to FIG. 74, step 2400 involves advancing theworking portion of an electrosurgical probe of the invention towards atarget tissue. As was noted hereinabove, the working portion of theprobe typically includes a plurality of working zones, each of which maybe characterized by a particular ablation rate and aspiration rate. Theterm “ablation rate” generally refers to an amount of tissue removed orvaporized per unit time; while the term “aspiration rate” usually refersto the rate at which one or more fluids may be aspirated from a givenregion. Such fluids may include body fluids, such as blood; extraneouslysupplied electrically conductive fluid, such as saline; a plasma, suchas a plasma derived from extraneously supplied saline; gaseous ablationby-products, or mixtures thereof. Typically, the working portion of theprobe comprises an electrically insulating electrode support, whereinthe electrode support is disposed on the distal end of a shaft, and aplurality of active electrodes are arranged on the electrode support.Each working zone typically has at least one aspiration port and atleast one of the plurality of active electrodes. The at least one activeelectrode of each working zone may be strategically located with respectto the at least one aspiration port.

[0377] Step 2402 involves positioning a first working zone of the probein at least close proximity to the target tissue. Usually, the firstworking zone is characterized as having a relatively high ablation rate,as compared with other working zones of the probe. As noted hereinabove,according to one aspect of the invention, ablation rate and aspirationrate are generally inversely related. That is to say, in general, aworking zone having a relatively low aspiration rate has a relativelyhigh ablation rate, and vice versa. This relationship is due, at leastin part, to the fact that a high aspiration rate in a working zoneprovides a localized (e.g., working zone-specific) environment which issomewhat inimical to the initiation and maintenance of a plasma thereat.

[0378] Step 2404 involves ablating at least a portion of the targettissue using the first working zone. The ablation performed in step 2404may be sufficiently rapid and aggressive that tissue fragments areresected from the target tissue via the molecular dissociation of tissuecomponents, in addition to the formation of low-molecular weightablation by-products. A portion of the low-molecular weight ablationby-products, together with some smaller resected tissue fragments, maybe aspirated directly from the surgical site via one or more aspirationports of the first working zone, step 2406. Other resected tissuefragments may be vaporized by the at least one active electrode of thefirst working zone, and the low-molecular weight ablation by-productsagain removed via one or more aspiration ports of the first workingzone.

[0379] Alternatively, or additionally, resected tissue fragments may bevaporized by at least one active electrode of the second working zone,step 2408. Thereafter, the low-molecular weight ablation by-productsresulting from step 2408 may be removed via one or more aspiration portsof the second working zone, step 2410. The second working zone typicallyhas a relatively high aspiration rate. Typically, the second workingzone has an ablation rate which is lower than that of the first workingzone, but which is nevertheless sufficient to vaporize resected tissuefragments. In this manner, blockage of the aspiration ports of thesecond working zone by tissue fragments is prevented.

[0380]FIG. 75A is a block diagram schematically representing anelectrosurgical system 2500, according to another embodiment of theinvention. System 2500 includes a probe 2501 having a shaft 2502, anactive electrode assembly 2520 coupled to shaft 2502, and an aspirationunit 2540. System 2500 further includes a high frequency power supply2528 coupled to active electrode assembly 2520. Active electrodeassembly 2520 is adapted for ablating or vaporizing at least one of: i)hard tissue, such as connective tissue in or around a synovial joint,and ii) soft tissue, such as adipose tissue, synovial fluid, and dermaltissue. Aspiration unit 2540 may be coupled to a suitable vacuum source2570. Aspiration unit 2540 and active electrode assembly 2520 may havethe elements described hereinbelow, e.g., with reference to FIGS. 75Band 75C, respectively.

[0381]FIG. 75B is a block diagram schematically representing anaspiration unit 2540′ of an electrosurgical apparatus or system.Aspiration unit 2540′ includes an aspiration tube 2546 coupled to anaspiration lumen 2544. Aspiration lumen 2544 is in turn coupled to asuction cavity 2543 of an electrode support 2522. Suction cavity 2543 isin communication with an aspiration port 2542. Aspiration tube 2546 isadapted for coupling to a vacuum source (e.g., FIG. 75A). According toone aspect of the invention, aspiration unit 2540′ may be a component ofan electrosurgical probe, e.g., probe 2900 (FIG. 79), wherein probe 2900is adapted for aspiration via aspiration unit 2540′ at a flow rate inthe range of from about 300 to 400 ml.min⁻¹. Although aspiration tube2546 and aspiration lumen 2544 are shown in FIG. 75B as separateelements, in alternative embodiments a single element may be coupledbetween suction cavity 2543 and the vacuum source.

[0382]FIG. 75C is a block diagram schematically representing an activeelectrode assembly 2520′ for an electrosurgical probe, according to theinvention. For example, active electrode assembly 2520′ may serve as acomponent of probe 2501 (FIG. 75A). Active electrode assembly 2520′includes an electrically insulating electrode support 2522, an activeelectrode screen 2508 disposed on electrode support 2522, and at leastone active electrode terminal 2510. Active electrode screen 2508 iselectrically isolated from active electrode terminal(s) 2510. In use,active electrode screen 2508 and active electrode terminal(s) 2510 areindependently coupled to a high frequency power supply (e.g., FIG. 75A).Typically, power from the power supply is supplied concurrently toactive electrode screen 2508 and active electrode terminal(s) 2510, withmost of the power being applied to active electrode screen 2508. In oneembodiment, at least about 65% of the power is applied to activeelectrode screen 2508, and often about 75% of the power is applied toactive electrode screen 2508.

[0383]FIG. 75D is a block diagram schematically representing anelectrode support 2522′ for an electrosurgical apparatus, according tothe invention. As an example, electrode support 2522′ may be a componentof active electrode assembly 2520 (FIG. 75A). Electrode support 2522′includes a treatment surface 2524, and a flow protection unit 2550. Flowprotection unit 2550 typically comprises a plurality of flow protectorsintegral with the electrode support and protruding from the treatmentsurface (e.g., FIGS. 76A-78). Electrode support 2522′ further includesan aspiration port 2542 within treatment surface 2524, and a suctioncavity 2543 in communication with aspiration port 2542. Typically,suction cavity 2543 is internal to electrode support 2522′ (e.g., FIG.77C).

[0384]FIG. 76A is a perspective view of an electrode support 2622,according to one embodiment of the invention. Electrode support 2622includes a first support end 2623 a, a second support end 2623 b, and atreatment surface 2624. A void within treatment surface 2624 defines anaspiration port 2642. As shown, aspiration port 2642 is approximatelyoval and is located substantially centrally on treatment surface 2624.However, other configurations for aspiration port 2642 are also withinthe scope of the invention. Electrode support 2622 further includes aplurality of flow protectors 2652 a-d. Typically, flow protectors 2652a-d are integral with, and comprise the same material as, electrodesupport 2622. As shown, flow protectors 2652 a-d are arranged in arectangular configuration, however other configurations are also withinthe scope of the invention. The configuration and dimensions of flowprotectors 2652 a-d may depend on a number of factors, such as: thedimensions of the treatment surface, the thickness of the activeelectrode screen, the size and shape of the aspiration port, and theflow rate of an aspiration stream drawn through aspiration port 2642.

[0385] Again with reference to FIG. 76A, electrode support 2622comprises an electrically insulating material, such as a ceramic, aglass, or a silicone rubber. In one embodiment, electrode support 2622comprises alumina. Electrode support 2622, including flow protectors2652 a-d, may be formed, for example, by a molding process. As shown,four flow protectors 2652 a-d are arranged in a rectangular pattern,wherein flow protectors 2652 a-d are contiguous with aspiration port2642. Similarly, FIG. 76A shows flow protectors 2652 a-d as extending tothe perimeter of treatment surface 2624. However as noted hereinabove,other numbers, shapes, and arrangements of flow protectors are alsopossible under the invention. Electrode support 2622 further includes aplurality of sockets 2626 a-d for accommodating a correspondingplurality of active electrode terminals (e.g., FIGS. 75C, 77A-C).Electrode support 2622 still further includes a pair of sockets 2626′a,2626′b for accommodating first and second leads of an active electrodescreen (e.g., FIGS. 80A-B). FIG. 76B is an end view of electrode support2622, showing flow protectors 2652 a, 2652 b protruding from treatmentsurface 2624, and suction cavity 2643 leading internally from second end2623 b. It should be understood that FIGS. 76A-B are diagrammaticrepresentations of an electrode support of the invention. In practice,sharp edges or corners may be eliminated in order to reduce the risk ofany inadvertent physical damage to a patient's tissue.

[0386]FIG. 77A is a plan view of an active electrode assembly 2720according to the instant invention. Active electrode assembly 2720comprises an electrode support 2722 including a treatment surface 2724,and a plurality of flow protectors 2752 a-d. As shown, treatment surface2724 is surrounded by a lip 2721. Active electrode assembly 2720 furtherincludes an active electrode screen 2708. Typically, active electrodescreen 2708 is disposed on treatment surface 2724. A void withintreatment surface 2724 defines an aspiration port 2742. Active electrodescreen 2708 has at least one screen void 2709 therein. Typically, activeelectrode screen 2708 has a plurality of screen voids 2709 aligned withaspiration port 2742. Screen voids 2709 allow the passage of gaseousablation by-products and any unwanted fluid from the vicinity oftreatment surface 2724 to aspiration port 2742, and at the same timeprevent aspiration port 2742 and other components from becoming cloggedwith debris. Furthermore, screen voids may provide sharp edges that areconducive to formation of a plasma thereat (see, e.g., FIG. 80B).

[0387] Again with reference to FIG. 77A, aspiration port 2742 is incommunication with a suction cavity 2743 internal to the electrodesupport (e.g. FIG. 77C). Aspiration port 2742 and suction cavity 2743represent a distal portion of an aspiration unit (e.g., FIGS. 75A-B). Inuse, the aspiration unit is in communication with a vacuum source, andablation byproducts, etc. are removed from the vicinity of treatmentsurface 2724 and screen 2708 via an aspiration stream. Flow protectors2752 a-d are located with respect to aspiration port 2742 such that eachflow protector 2752 a-d defines a shielded region of active electrodescreen 2708, wherein each shielded region is characterized by arelatively low flow rate of the aspiration stream towards aspirationport 2742 (see, e.g., FIG. 78).

[0388] Active electrode assembly 2720 further includes a plurality ofactive electrode terminals 2710 a-d protruding from treatment surface2724 (FIG. 77B). Each active electrode terminal 2710 a-d is electricallyisolated from active electrode screen 2708. Typically, each activeelectrode terminal 2710 a-d is in the form of a wire comprising a metalselected from the group consisting of molybdenum, platinum, tungsten,palladium, iridium, titanium,tantalum, stainless steel or their alloys.In one embodiment, each active electrode terminal 2710 a-d is a wirecomprising at least about 90% molybdenum.

[0389] Each active electrode terminal 2710 a-d is adapted foraggressively ablating a target tissue, including hard connective tissue,from a surgical site. For example, active electrode terminals 2710 a-dmay be used to rapidly remove ligament, tendon, cartilage, or bonetissue in or around a joint. Due to the aggressive nature of tissueablation, active electrode terminals 2710 a-d may dislodge tissuefragments which are too large to readily pass through screen voids 2709.Active electrode screen 2708 is adapted for digesting or vaporizing suchresected tissue fragments, e.g., via plasma-induced moleculardissociation of the tissue components. Active electrode screen 2708 isfurther adapted for removing soft tissue from a surgical site. In use,active electrode terminals 2710 a-d and active electrode screen 2708 areindependently coupled to a high frequency power supply. Typically, mostof the power is supplied to active electrode screen 2708, and oftenabout 75% of the power is supplied to active electrode screen 2708.

[0390]FIG. 77B is a side view of active electrode assembly 2720 of FIG.77A. Lip 2721 lies at an angle ø with respect to treatment surface 2724,wherein angle ø is typically in the range of from about 60° to 85°, moretypically from about 70° to 85°, and often about 80°. Lip 2721 confers amore user-friendly configuration, and often facilitates access ofassembly 2720 to a target tissue. Active electrode screen 2708 typicallyhas a thickness, T_(s) in the range of from about 0.0015 to 0.006 inch,more typically from about 0.002 to 0.004, and often from about 0.0025 to0.0035 inch. Flow protectors 2752 a-d each protrude from treatmentsurface 2724 by a distance H_(p), wherein H_(p) is typically in therange of from about 0.006 to 0.018 inch, more typically from about 0.009to 0.015 inch, and often about 0.012 inch. Typically, the ratioH_(p):T_(s) is at least about 2:1, more typically at least about 3:1,and often in the range of from about 3:1 to 5:1. Active electrodeterminals 2710 a-d protrude from treatment surface 2724 by a distanceH_(t), wherein H_(t) is typically in the range of from about 0.012 to0.025 inch, more typically from about 0.015 to 0.020 inch, and oftenabout 0.018 inch. The distance Ht is typically greater than the distanceHp. In one embodiment, H_(t)>H_(p) by about 0.005 inch.

[0391]FIG. 77C is an end view of active electrode assembly 2720 takenalong the lines 77C-77C of FIG. 77A. A suction cavity 2743 lies internalto electrode support 2722. Aspiration port 2742 is in communication withsuction cavity 2743. Active electrode terminals 2710 a, 2710 b extendabove flow protectors 2752 a, 2752 b, respectively. Active electrodeterminals 2710 a, 2710 b are in communication with active electrodeleads 2711 a, 2711 b, respectively. (Active electrode terminals 2710 c-d(FIG. 77A) are similarly coupled to corresponding active electrode leads(not shown in FIG. 77C).) In one embodiment, active electrode leads 2711a, 2711 b couple active electrode terminals 2710 a, 2710 b, respectivelyto a connection block (e.g., FIG. 79), to facilitate connection of theactive electrode terminals to a high frequency power supply. In oneembodiment, active electrode leads 2711 a, 2711 b each comprise a lengthof insulated wire, and active electrode terminals 2710 a, 2710 b eachcomprise a terminal portion of the wire from which the insulation hasbeen removed. In one embodiment, active electrode terminals 2710 a, 2710b each comprise a length of naked (uninsulated) molybdenum wire. Eachactive electrode terminal 2710 a, 2710 b typically has a diameter in therange of from about 0.010 to 0.020 inch, more typically from about 0.012to 0.018 inch, and often about 0.015 inch. Active electrode screen 2708is omitted from FIG. 77C for the sake of clarity.

[0392]FIG. 78 schematically represents an active electrode screen 2808on a treatment surface 2824 of an active electrode assembly 2820, asseen in plan view. A pair of flow protectors are represented as 2852 a,2852 b. As an example, active electrode assembly 2820 may be a componentof an electrosurgical catheter or probe (e.g., FIG. 75A, FIG. 79).During use of assembly 2820, ablation by-products and other unwantedmaterials may be removed from the vicinity of treatment surface 2824 inan aspiration stream via an aspiration unit (e.g., FIG. 75B). Typically,the aspiration unit includes an aspiration port (e.g., FIG. 76A) withinthe treatment surface. The centripetal direction of flow of anaspiration stream towards the aspiration port is indicated in FIG. 78 byopen arrows. (The aspiration port is omitted from FIG. 78 for the sakeof clarity.) Two shielded regions of screen 2808 are shown as shadedareas. Thus, first and second shielded regions 2807 a, 2807 b,respectively are located centripetally with respect to flow protectors2852 a, 2852 b, respectively. First and second shielded regions 2807 a,2807 b represent regions of relatively low flow rate, as compared withthe remaining, non-shielded regions of screen 2808. Applicant hasdetermined that a lower flow rate over shielded regions of screen 2808is associated with facile initiation and maintenance of a plasma at theregions of relatively low flow rate. Applicant has further determinedthat facile initiation and maintenance of a plasma at or adjacent toscreen 2808 promotes tissue ablation by active electrode assembly 2820.Thus, the presence of flow protectors protruding from treatment surface2824 results in more aggressive ablation of tissue, for example, viaplasma induced molecular dissociation of tissue components (e.g.,Coblation®)

[0393]FIG. 79 schematically represents an electrosurgical probe 2900,according to one embodiment of the invention. Probe 2900 includes ashaft 2902 having a shaft distal end 2902 a, a shaft proximal end 2902b, and a handle 2904 housing a connection block 2905. An activeelectrode assembly 2920 is disposed at shaft distal end 2902 a. Activeelectrode assembly 2920 includes an electrically insulating electrodesupport 2922 having a treatment surface 2924 and a plurality of flowprotectors 2952. The role of flow protectors in promoting plasmaformation was described hereinabove (e.g., with reference to FIG. 78).Active electrode assembly 2920 further includes a plurality of activeelectrode terminals 2910 protruding from treatment surface 2924. Anaspiration port 2942 is located within treatment surface 2924.Aspiration port 2942 leads to a suction cavity internal to support 2922,and the suction cavity is in communication with an aspiration lumen orelement (not shown in FIG. 79). Typically, the aspiration lumen lieswithin shaft 2902 (e.g., generally as shown in FIG. 70A).

[0394] Again with reference to FIG. 79, shaft 2902 may comprise anelectrically conducting material, e.g., stainless steel, or other metalsand their alloys. An electrically insulating sleeve 2918 (e.g.,comprising a plastic) encases a proximal portion of shaft 2902. In oneembodiment, probe 2900 includes an electrically conducting cap 2903continuous with shaft distal end 2902 a. A return electrode 2914partially surrounds active electrode assembly 2920, and comprises cap2903 and an exposed (non-insulated) distal portion of shaft 2902.Connection block 2905 is adapted for independently coupling returnelectrode 2914, active electrode terminals 2910, and an active electrodescreen to a high frequency power supply (e.g., FIG. 75A). The activeelectrode screen (e.g., FIGS. 77A, 80A-B) is omitted from FIG. 79 forthe sake of clarity.

[0395]FIG. 80A is a side view, and FIG. 80B is a perspective view, of anactive electrode screen 3008, according to one embodiment of theinvention. Screen 3008 comprises a metal plate 3002 including a centralportion 3010 having a plurality of screen voids 3009 therein. As shown,three screen voids 3009 within central portion 3010 each have adiamond-like shape. However, it is to be understood that the inventionis by no means limited to this number and shape of screen voids, andother numbers and configurations of such screen voids are also withinthe scope of the invention. In one embodiment, plate 3002 has athickness in the range of from about 0.0015 to 0.006 inch, and oftenfrom about 0.0025 to 0.0035 inch.

[0396] Again with reference to FIGS. 80A-B, plate 3002 includes a firstside 3002 a and a second side 3002 b, together with first and secondarms 3008 a, 3008 b, respectively, and first and second ends 3012 a,3012 b, respectively. Each of first and second ends 3012 a, 3012 binclude a screen void 3009′. Plate 3002 has a width, Ws, generally inthe range of from about 0.05 to 0.2 inch, and more typically from about0.075 to 0.15 inch. Plate 3002 has a length, Ls, typically in the rangeof from about 0.05 to 0.3 inch, and more typically from about 0.075 to0.15 inch. In use, plate 3002 is disposed on an electrode support, suchthat: second side 3002 b opposes a treatment surface of the electrodesupport, screen voids 3009/3009′ are aligned with an aspiration port ofthe electrode support, and first side 3002 a is exposed (e.g., exposedto a target tissue and/or to the flow of an aspiration stream).

[0397] Active electrode screen 3008 further includes a relatively short,first screen lead 3004, and a longer, second screen lead 3006. Thelocations of attachment of first and second screen lead 3004, 3006 tosecond side 3002 b of plate 3002 are indicated as 3004′, 3006′,respectively (FIG. 80B). First screen lead 3004 typically has a lengthin the range of from about 0.1 to 1.0 inch, and more typically fromabout 0.2 to 0.5 inch. First screen lead 3004 typically terminates in a“free” end within the electrode support. Second screen lead 3006typically has a length in the range of from about 6 to 12 inches, andmore typically in the range of from about 7 to 9 inches. Second screenlead 3006 is typically connected to a connection block (e.g., FIG. 79),to allow plate 3002 to be coupled to a high frequency power supply(e.g., FIG. 75A). First and second screen leads 3004, 3006 may eachcomprise a wire, such as platinum wire.

[0398] Plate 3002 includes a plurality of sharp edges and a number ofpointed projections, e.g., on first and second ends 3012 a, 3012 b.Applicant has observed that the sharp edges and pointed projections ofscreen 3008 strongly promote generation of a plasma in the vicinity ofplate 3002, upon application of a high frequency voltage thereto. Whilenot being bound by theory, the facile generation of a plasma in thevicinity of plate 3002 allows the aggressive ablation of hard or firmtissue from a surgical site, such as in or around a joint (e.g., theknee, the shoulder, etc.). Plate 3002 may comprise a metal such asmolybdenum, platinum, tungsten, palladium, iridium, titanium,tantalum,stainless steel or their alloys. In one embodiment, plate 3002 comprisesan alloy of platinum and iridium, typically comprising from about 70% to99% platinum and from about 30% to 1% iridium, more typically from about80% to 95% platinum and from about 20% to 5% iridium, and often about90% platinum and about 10% iridium.

[0399]FIG. 81 schematically represents a series of steps involved in amethod of ablating tissue using an electrosurgical apparatus of theinvention, wherein step 3100 involves positioning an active electrodeassembly in at least close proximity to a target tissue to be ablated.Typically, the active electrode assembly is disposed at the distal endof a shaft of the electrosurgical apparatus (for example, a catheter orprobe, e.g., FIG. 79). The active electrode assembly includes at leastone active electrode terminal adapted for aggressively removingrelatively hard target tissue. The active electrode assembly alsoincludes an active electrode screen adapted for digesting tissuefragments and for ablating relatively soft tissue. The active electrodescreen is electrically isolated from the active electrode terminal(s).During use of the apparatus, each active electrode terminal and theactive electrode screen are coupled to a high frequency power supply.The high frequency power supply is adapted for operation in at least theablation mode. The active electrode screen includes one or more screenvoids adapted for preventing resected tissue fragments, havingdimensions greater than the dimensions of the screen void(s), fromentering and clogging the probe or catheter.

[0400] The active electrode screen and the at least one active electrodeterminal are mounted on an electrically insulating electrode support.The apparatus further includes at least one flow protector protrudingfrom a treatment surface of the electrode support. Typically, the flowprotector(s) are located at or beyond the perimeter of the activeelectrode screen. Each flow protector defines a shielded region of theactive electrode screen. Each shielded region is characterized by havinga relatively low flow rate of an aspiration stream, as compared with anon-shielded region of the active electrode screen, such that eachshielded region is adapted for the facile initiation and maintenance ofa plasma thereat, upon application of a high frequency voltage betweenthe active electrode screen and a return electrode. Typically, thereturn electrode is disposed at the shaft distal end and is coupled tothe high frequency power supply.

[0401] Step 3102 involves applying a high frequency voltage, from thehigh frequency power supply, between the active electrode screen and areturn electrode, and concurrently therewith, applying a high frequencyvoltage between each active electrode terminal and the return electrode.Typically, the active electrode screen receives from about 65% to 75% ofthe power, while the active electrode terminal(s) receive from about 35%to 25% of the power. The actual voltage parameters are generally withinthe ranges cited hereinabove for the ablation mode, for example, in therange of from about 200 volts RMS to about 1800 volts RMS. In someembodiments, an extraneous electrically conductive fluid, e.g., isotonicsaline, may be delivered to the surgical site and/or to the activeelectrode assembly during step 3102. In other embodiments, the surgicalsite may be inherently replete with intrinsic (bodily) fluids, such asblood, synovial fluid, thus obviating the use of extraneous fluid.

[0402] Step 3104 involves ablating target tissue by the active electrodeterminal(s) as a result of the high frequency voltage applied in step3102. In one embodiment, the tissue ablated by the active electrodeterminal(s) comprises hard or firm tissue, such as ligament, cartilage,tendon, or bone. Step 3106 involves digesting any resected tissuefragments, e.g., fragments of tissue released at or near the surgicalsite as a result of step 3104. Such resected tissue fragments may bedrawn over an exposed surface of the active electrode screen by anaspiration stream (e.g., step 3110), and such tissue fragments may bedigested on, or adjacent to, the active electrode screen by the highfrequency voltage of step 3102.

[0403] Step 3108 involves ablating or removing target tissue from thesurgical site using the active electrode screen, as a result of the highfrequency voltage applied to the active electrode screen in step 3102.Typically, the target tissue removed by the active electrode screencomprises relatively soft tissue, such as fatty tissue, synovial fluid,or dermal tissue. Optionally, the electrosurgical apparatus may bemanipulated (e.g., by axial translation) during application of the highfrequency voltage to effect the controlled removal of target tissue. Itshould be understood that the apparatus may perform two or more of steps3104, 3106, and 3108 concurrently, depending on the nature of the targettissue, the type of procedure, etc.

[0404] Step 3110 involves aspirating unwanted materials, e.g., gaseousablation byproducts, from the surgical site, or from the vicinity of theactive electrode assembly, via an aspiration stream. In one embodiment,the aspiration stream has a relatively high flow rate, in the range offrom about 150 ml.min⁻¹ to 400 ml.min⁻¹. Applicant has found that theconfiguration of the active electrode assembly, and in particular theinclusion of flow protectors on the treatment surface, allows plasmaformation and efficient electrosurgical removal of target tissue whileusing such a high flow rate. Typically, the aspiration stream is drawnproximally by suction from a vacuum source coupled to the proximal endof an aspiration unit. In one embodiment, the aspiration unit includes aproximal aspiration tube adapted for coupling to the vacuum source, andan aspiration lumen coupled between the aspiration tube and the activeelectrode assembly. Unwanted materials removed from the surgical sitemay be sequestered in a trap, as is well known in the art.

[0405] Other modifications and variations can be made to the disclosedembodiments without departing from the subject invention. For example,other numbers and arrangements of the flow protectors, aspiration port,active electrode screen, and active electrode terminal(s) of the activeelectrode assembly are possible. Similarly, numerous other methods ofablating or otherwise treating tissue using electrosurgical apparatus ofthe invention will be apparent to the skilled artisan. Thus, while theexemplary embodiments of the present invention have been described indetail, by way of example and for clarity of understanding, a variety ofchanges, adaptations, and modifications will be obvious to those ofskill in the art. Therefore, the scope of the present invention islimited solely by the appended claims.

What is claimed is:
 1. An electrosurgical probe for treating a targettissue at a surgical site, comprising: a shaft having a shaft distal endand a shaft proximal end; and an active electrode assembly disposed atthe shaft distal end, wherein the active electrode assembly includes anelectrically insulating electrode support and an active electrodescreen, the electrically insulating electrode support including at leastone flow protector and a treatment surface, the at least one flowprotector protruding from the treatment surface, and the activeelectrode screen disposed on the treatment surface of the electricallyinsulating electrode support.
 2. The probe of claim 1, furthercomprising an aspiration unit including a suction cavity and anaspiration lumen, the suction cavity internal to the electrode support,the aspiration lumen in communication distally with the suction cavity,and the aspiration unit adapted for removing ablation by-products fromthe vicinity of the active electrode assembly via an aspiration stream.3. The probe of claim 2, wherein the aspiration lumen is coupled at itsproximal end to an aspiration tube, and the aspiration tube is adaptedfor coupling to a vacuum source.
 4. The probe of claim 2, wherein theaspiration stream has a flow rate through the aspiration unit in therange of from about 150 ml.min⁻¹ to 400 ml.min⁻¹.
 5. The probe of claim1, wherein the at least one flow protector comprises an electricallyinsulating material selected from the group consisting of a ceramic, aglass, and a silicone rubber.
 6. The probe of claim 1, wherein the atleast one flow protector is integral with the electrically insulatingelectrode support.
 7. The probe of claim 1, wherein the at least oneflow protector protrudes from the treatment surface by a distance atleast twice the thickness of the active electrode screen.
 8. The probeof claim 1, wherein the at least one flow protector protrudes from thetreatment surface by a distance about three times the thickness of theactive electrode screen.
 9. The probe of claim 1, wherein each flowprotector causes preferential flow of an aspiration stream over anexposed surface of the active electrode screen.
 10. The probe of claim9, wherein each flow protector shields a shielded region of the exposedsurface of the active electrode screen from the flow of the aspirationstream, wherein each shielded region lies between a corresponding flowprotector and an aspiration port, the aspiration port located within thetreatment surface.
 11. The probe of claim 10, wherein each flowprotector defines a corresponding one of the shielded regions, whereineach shielded region is characterized by a lower flow rate of theaspiration stream than a non-shielded region of the exposed surface ofthe active electrode screen.
 12. The probe of claim 10, wherein eachshielded region promotes the generation and maintenance of a plasmathereat.
 13. The probe of claim 1, wherein the active electrode screenincludes a first screen lead and a second screen lead.
 14. The probe ofclaim 13, wherein the first screen lead terminates in a free end withinthe electrode support.
 15. The probe of claim 14, wherein the secondscreen lead is coupled to a connection block, the connection blockadapted for coupling the active electrode screen to a high frequencypower supply.
 16. The probe of claim 1, wherein the active electrodescreen is disposed on the treatment surface of the electrode support.17. The probe of claim 1, wherein the active electrode screen has aplurality of voids therein.
 18. The probe of claim 1, wherein the activeelectrode screen comprises an alloy of platinum and iridium.
 19. Theprobe of claim 1, wherein the active electrode assembly furthercomprises at least one active electrode terminal.
 20. The probe of claim19, wherein the at least one active electrode terminal comprises amaterial selected from the group consisting of molybdenum, platinum,tungsten, palladium, iridium, titanium,tantalum, stainless steel, andtheir alloys.
 21. The probe of claim 19, wherein the at least one activeelectrode terminal comprises four active electrode terminals, eachactive electrode terminal protruding from the treatment surface.
 22. Theprobe of claim 19, wherein the four active electrode terminals arearranged in a substantially rectangular pattern.
 23. The probe of claim19, wherein the at least one active electrode terminal comprises aplurality of active electrode terminals, each of the plurality of activeelectrode terminals spaced from the at least one flow protector.
 24. Theprobe of claim 19, wherein the at least one active electrode terminal iselectrically isolated from the active electrode screen.
 25. The probe ofclaim 19, further comprising an active electrode lead coupled to eachactive electrode terminal.
 26. The probe of claim 19, wherein the atleast one active electrode terminal comprises a molybdenum wire having adiameter in the range of from about 0.010 to 0.020 inch.
 27. The probeof claim 19, wherein the at least one active electrode terminalcomprises a plurality of active electrode terminals, each of theplurality of active electrode terminals arranged orthogonal to thetreatment surface of the electrode support.
 28. The probe of claim 1,further comprising a return electrode.
 29. The probe of claim 28,further comprising an electrically conducting cap at the shaft distalend, wherein the electrode support is mounted in the cap, and whereinthe return electrode comprises the cap.
 30. The probe of claim 29,wherein the cap is in electrical communication with the shaft.
 31. Theprobe of claim 1, wherein a proximal portion of the shaft is encasedwithin an electrically insulating sleeve.
 32. The probe of claim 1,wherein the electrode support includes an internal suction cavity incommunication with an aspiration port.
 33. The probe of claim 32,wherein the aspiration port comprises a void within the treatmentsurface.
 34. The probe of claim 1, further comprising a connection blockadapted for coupling the probe to a high frequency power supply, theconnection block independently coupled to a return electrode, the activeelectrode screen, and at least one active electrode terminal.
 35. Theprobe of claim 34, further comprising a handle, the connection blockhoused within the handle.
 36. The probe of claim 1, wherein theelectrode support comprises a ceramic, a glass, or a silicone rubber.37. The probe of claim 1, wherein the electrode support comprisesalumina.
 38. An electrosurgical probe, comprising: a shaft having ashaft distal end and a shaft proximal end; an electrode support disposedat the shaft distal end, the electrode support including a treatmentsurface, at least one flow protector protruding from the treatmentsurface, and a suction cavity within the electrode support; at least oneactive electrode terminal protruding from the treatment surface; and anactive electrode screen disposed on the treatment surface.
 39. The probeof claim 38, wherein the active electrode screen includes a centralportion having at least one screen void.
 40. The probe of claim 39,further comprising an aspiration port within the treatment surface, theat least one screen void aligned with the aspiration port.
 41. The probeof claim 38, wherein the active electrode screen includes a first sideexposed to flow of an aspiration stream and a second side opposing thetreatment surface.
 42. The probe of claim 41, wherein each flowprotector defines a shielded region of the first side of the activeelectrode screen, wherein each shielded region is adapted for enhancedplasma formation thereat.
 43. The probe of claim 38, wherein the atleast one active electrode terminal extends beyond the at least one flowprotector by a distance in the range of from about 0.003 to 0.010 inch.44. The probe of claim 38, wherein the at least one active electrodeterminal comprises four active electrode terminals.
 45. The probe ofclaim 38, wherein the at least one active electrode terminal has adiameter in the range of from about 0.010 to 0.020 inch.
 46. The probeof claim 38, wherein the at least one active electrode terminalcomprises molybdenum wire.
 47. The probe of claim 38, further comprisinga return electrode and an electrically insulating sleeve on a proximalportion of the shaft, wherein the shaft comprises an electricallyconducting material, and the return electrode comprises an exposeddistal portion of the shaft.
 48. The probe of claim 38, wherein theshaft comprises a material selected from the group consisting ofstainless steel, molybdenum, platinum, tungsten, palladium, iridium,titanium,tantalum, stainless steel and their alloys.
 49. Anelectrosurgical probe, comprising: a shaft having a shaft distal end anda shaft proximal end; an electrode support disposed at the shaft distalend, the electrode support including a treatment surface, and at leastone flow protector protruding from the treatment surface; an aspirationunit including a suction cavity and an aspiration port, the suctioncavity internal to the electrode support, and wherein a void in thetreatment surface defines the aspiration port; at least one activeelectrode terminal protruding from the treatment surface; and an activeelectrode screen disposed on the treatment surface, wherein each flowprotector defines a shielded region of the active electrode screen, theshielded region adapted for promoting plasma formation by the activeelectrode screen.
 50. The probe of claim 49, wherein the at least oneactive electrode terminal is substantially cylindrical in shape.
 51. Theprobe of claim 49, wherein the at least one active electrode terminalcomprises a length of molybdenum wire.
 52. The probe of claim 49,wherein the active electrode screen comprises a platinum/iridium alloyplate having at least one void therein.
 53. The probe of claim 49,wherein the at least one flow protector comprises a protrusion of thetreatment surface.
 54. The probe of claim 49, wherein each flowprotector is integral with the electrode support.
 55. The probe of claim49, wherein each flow protector comprises an electrically insulatingmaterial.
 56. The probe of claim 49, wherein each flow protector extendsfrom the treatment surface by a distance in the range of from about0.006 to 0.020 inch.
 57. The probe of claim 49, wherein each flowprotector is arranged substantially orthogonal to the treatment surface.58. An electrosurgical system, comprising: an electrosurgical probeincluding a shaft having a shaft distal end and a shaft proximal end, anactive electrode assembly disposed at the shaft distal end, and a returnelectrode, the active electrode assembly comprising an electricallyinsulating electrode support having a treatment surface, an activeelectrode screen disposed on the treatment surface, and at least oneactive electrode terminal protruding from the treatment surface, the atleast one active electrode terminal electrically isolated from theactive electrode screen, and the electrode support including at leastone flow protector protruding from the treatment surface; and a highfrequency power supply independently coupled to the active electrodescreen and to the at least one active electrode terminal.
 59. An activeelectrode assembly, comprising: an electrode support having a treatmentsurface; an active electrode screen disposed on the treatment surface;at least one flow protector protruding from the treatment surface, theat least one flow protector extending beyond the active electrodescreen; and at least one active electrode terminal protruding from thetreatment surface, the at least one active electrode terminalelectrically isolated from the active electrode screen.
 60. The activeelectrode assembly of claim 59, wherein the active electrode screen hasa thickness, Ts, and the at least one flow protector extends from thetreatment surface by a distance, Hp, wherein the ratio Hp:Ts aspirationport is in the range of from about 3:1 to 5:1.
 61. The active electrodeassembly of claim 59, wherein each active electrode terminal and the atleast one flow protector extend from the treatment surface by distancesHt and Hp, respectively, wherein Ht is greater than Hp.
 62. The activeelectrode assembly of claim 61, wherein the distance Ht is about 0.005inch greater than the distance Hp.
 63. The active electrode assembly ofclaim 60, wherein the thickness, Ts of the active electrode screen is inthe range of from about 0.002 to 0.005 inch.
 64. The active electrodeassembly of claim 59, wherein the treatment surface has a void therein,and the void defines an aspiration port.
 65. The active electrodeassembly of claim 64, further comprising a suction cavity within theelectrode support, wherein the suction cavity is in communication withthe aspiration port.
 66. The active electrode assembly of claim 59,wherein the electrode support comprises a material selected from thegroup consisting of a ceramic, a glass, and a silicone rubber.
 67. Theactive electrode assembly of claim 59, wherein the at least one activeelectrode terminal is arranged substantially orthogonal to the treatmentsurface.
 68. The active electrode assembly of claim 59, wherein the atleast one active electrode terminal comprises a material selected fromthe group consisting of molybdenum, platinum, tungsten, palladium,iridium, titanium,tantalum, stainless steel and their alloys.
 69. Theactive electrode assembly of claim 59, wherein the at least one activeelectrode terminal comprises a plurality of active electrode terminals.70. The active electrode assembly of claim 69, wherein each of theplurality of active electrode terminals comprises molybdenum wire. 71.An active electrode screen for an electrosurgical probe, comprising: ametal plate including a first arm, a second arm, a central portionbetween the first and second arms, a first end and a second end, thefirst and second ends extending in opposite directions from the centralportion, each of the first and second ends having at least one pointedprojection emanating therefrom, and the central portion having at leastone void therein; and at least one screen lead coupled to the metalplate.
 72. The active electrode screen of claim 71, wherein the at leastone lead comprises a first screen lead connected to the first arm and asecond screen lead connected to the second arm.
 73. The active electrodescreen of claim 72, wherein the metal plate has a first side and asecond side, and wherein the first and second screen leads are connectedto the second side of the plate.
 74. The active electrode screen ofclaim 72, wherein the first screen lead is shorter than the secondscreen lead.
 75. The active electrode screen of claim 74, wherein thefirst screen lead has a length in the range of from about 0.1 to 1.0inch.
 76. The active electrode screen of claim 74, wherein the secondlead has a length in the range of from about 6 to 12 inches.
 77. Theactive electrode screen of claim 71, wherein the metal plate comprisesplatinum and iridium.
 78. The active electrode screen of claim 71,wherein the metal plate has a thickness in the range of from about 0.002to 0.005 inch.
 79. The active electrode screen of claim 71, wherein themetal plate has a length in the range of from about 0.05 inch to 0.30inch, and wherein the metal plate has a width in the range of from about0.05 inch to 0.20 inch.
 80. The active electrode screen of claim 71,wherein each of the first and second arms has a void therein.
 81. Amethod for removing a target tissue at a surgical site, comprising: a)providing an electrosurgical probe having an active electrode assemblyand a return electrode, the active electrode assembly comprising anactive electrode screen disposed on a treatment surface of anelectrically insulating electrode support, at least one flow protectorprotruding from the treatment surface, and a plurality of activeelectrode terminals protruding from the treatment surface, each of theplurality of active electrode terminals electrically isolated from theactive electrode screen; b) positioning the active electrode assembly inat least close proximity to the target tissue; and c) applying a highfrequency voltage between the active electrode screen and the returnelectrode and between the plurality of active electrode terminals andthe return electrode, wherein at least a portion of the target tissue isablated or modified.
 82. The method of claim 81, wherein said step c)comprises applying the high frequency voltage concurrently to both theactive electrode screen and to the plurality of active electrodeterminals.
 83. The method of claim 82, wherein during said step c) atleast about 65% of the power is applied to the active electrode screen.84. The method of claim 81, wherein during said step c) the activeelectrode screen is adapted for removing soft tissue from a patient. 85.The method of claim 84, wherein the plurality of active electrodeterminals are adapted for aggressively removing the target tissue, andthe active electrode screen is further adapted for digesting resectedfragments of the target tissue.
 86. The method of claim 81, whereinduring said step c) the active electrode terminals are adapted forablating connective tissue selected from the group consisting ofligament, cartilage, tendon, and bone.
 87. The method of claim 81,further comprising: d) aspirating unwanted materials from the surgicalsite in an aspiration stream.
 88. The method of claim 87, wherein theaspiration stream flows at a volume in the range of from about 150ml.min⁻¹ to 400 ml.min⁻¹.
 89. The method of claim 87, wherein the probeincludes an aspiration unit, and the unwanted materials are aspiratedfrom the surgical site via the aspiration unit.
 90. The method of claim89, wherein the aspiration unit includes an aspiration port within thetreatment surface, a suction cavity located within the electrodesupport, the aspiration port leading to the suction cavity, and anaspiration lumen in communication distally with the suction cavity. 91.The method of claim 90, wherein the aspiration tube is coupledproximally to a vacuum source.
 92. The method of claim 87, wherein theat least one flow protector defines a shielded region of the activeelectrode screen, wherein a first flow rate of the aspiration streamover the shielded region is lower than a second flow rate of theaspiration stream over a non-shielded region of the active electrodescreen.
 93. The method of claim 92, wherein a relatively low flow rateof the aspiration stream in the shielded region promotes generation andmaintenance of a plasma at the shielded region upon application of thehigh frequency voltage of said step c).
 94. The method of claim 81,wherein the at least one active electrode terminal is adapted forablating the target issue via molecular dissociation of components ofthe target tissue.
 95. The method of claim 81, further comprising: e)during said step c), manipulating the active electrode assembly withrespect to the target tissue, wherein the target tissue is ablated. 96.The method of claim 81, further comprising: f) prior to or during saidstep c), delivering an electrically conductive fluid to the activeelectrode assembly or to the surgical site.
 97. The method of claim 81,wherein the high frequency voltage applied in said step c) is in therange of from about 200 volts RMS to 1800 volts RMS.
 98. The method ofclaim 81, wherein during said step c) the target tissue is exposed to atemperature in the range of from about 40° C. to 90° C.
 99. A method forablating a target tissue at a surgical site of a patient, comprising: a)providing an electrosurgical probe including a return electrode and anactive electrode assembly, the active electrode assembly including atleast one active electrode terminal and an active electrode screen, theactive electrode screen disposed on a treatment surface of anelectrically insulating electrode support, the electrode supportincluding a flow protection unit for providing differential flow of anaspiration stream on a first side of the active electrode screen; b)positioning the active electrode assembly in at least close proximity tothe target tissue; c) applying a high frequency voltage concurrently tothe at least one the active electrode terminal and to the activeelectrode screen, the high frequency voltage sufficient to ablate atleast a portion of the target tissue; and d) aspirating unwantedmaterials from the surgical site, wherein the unwanted materials areaspirated via an aspiration port and a suction cavity, the aspirationport within the treatment surface and the suction cavity internal to theelectrode support.
 100. The method of claim 99, wherein the surgicalsite lies within a synovial joint.
 101. The method of claim 99, whereinthe surgical site lies within the vertebral column.
 102. The method ofclaim 99, further comprising: e) during said step c), reciprocating theactive electrode assembly with respect to the target tissue, wherein thetarget tissue is ablated.
 103. The method of claim 99, wherein thetarget tissue comprises a material selected from the group consisting ofcartilage, ligament, tendon, and bone.